The larger specimen of Sinopterus atavismus enters the LPT basal to dsungaripterids

Many pterosaur fossils attributed to Sinopterus
have been described. They vary greatly in size and shape.

Presently four Sinopterus specimens have been added
to the large pterosaur tree (LPT, 253 taxa). They are all sister taxa, but as in Archaeopteryx, no two are alike, one is basal to the others, which are, in turn, basal to large clades within the Tapejaridae.

  1. Sinopterus dongi (the holotype) nests basal to the Tupuxuara clade.
  2. Sinopterus liui nests in the Tupuxuara clade.
  3. Sinopterus jii (aka Huaxiapterus jii) nests basal to the Tapejara clade.
  4. Sinopterus atavisms (Figs. 1-4; Zhang et al. 2019; IVPP V 23388) nests basal to the Dsungaripterus (Fig. 4) clade, outside the Tapejaridae.

Figure 1. Sinopterus atavismus in situ.

Figure 1. Sinopterus atavismus in situ. IVPP V 23388

From the Zhang et al. 2019 abstract:
“Here, we report on a new juvenile specimen of Sinopterus atavismus from the Jiufotang Formation of western Liaoning, China, and revise the diagnosis of this species.”

Zhang et al. note that several elements are unfused including a humeral epiphysis. Several pits and grooves in the distal ends of the long bones are also pitted and grooved. Normally these would be good indicators in archosaurs and mammals, but pterosaurs are lepidosaurs and lepidosaurs follow distinctly different ‘rules’ for growth (Maisano 2002). As an example, some pterosaur embryos have fused elements. Some giant pterosaurs have unfused elements. Here the new specimen (IVPP 23388) is considered an ontogenetic adult as its size is similar to other phylogenetic relatives.

“Sinopterus atavismus does not present a square-like crest. Moreover the feature that groove in the ventral part of the second or third phalanx of manual digit IV is not diagnostic of the species.”

Zhang et al. are comparing the new larger IVPP specimen to the smaller, previously described (Lü et al. 2016) XHPM 1009 specimen (then named Huaxiapterus atavismus), which they considered conspecific. The XHPM specimen has wing phalanx grooves while the IVPP specimen does not. The shapes of the skulls do not match (Fig. 3) and we know that pterosaurs grew isometrically. Thus these two specimens are not conspecific.

“In the new material, the skull preserves a pointed process in the middle part of the dorsal marginof the premaxillary crest, which is different from other Chinese tapejarids. Considering the new specimen is known from a large skeleton that differed from the holotype, this difference may be related to ontogeny, as the premaxillary crest of the holotype is short and does not extend as long as that of the new specimen.”

These two specimens are not conspecific, so ontogenetic comparisons should not be made.

Figure 2. Sinopterus atavismus reconstruction.

Figure 2. Sinopterus atavismus reconstruction.

From the Zhang et al. 2019 discussion:
“Except for D 2525 which represents an adult individual of Sinopterus (Lü et al. 2006b), all Chinese tapejarid pterosaurs known so far were immature individuals at the time of death. The new specimen (IVPP 23388) shares some features with the holotype of Sinopterus atavismus. The wingspan of the new material is about twice as long as that of the holotype of S. atavismus.”

As mentioned above, the IVPP V 23388 specimen is here considered an adult with unfused bone elements. It needs both a new generic and specific name. The XHPM 1009 specimen (Fig. 3) requires further study.

Figure 3. Sinopterus atavismus size comparison

Figure 3. Sinopterus atavismus size and shape comparison.

The present confusion about the ontogenetic status of pterosaurs 
could have been largely resolved with the publication of “The first juvenile Rhamphorhynchus recovered by phylogenetic analysis” and other papers suppressed by pterosaur referees. Sorry, readers, we’ll have to forge ahead with the venues we have.

Figure 3. Sinopterus atavismus skull restored (gray areas).

Figure 4. Sinopterus atavismus skull restored (gray areas).

Figure 4. Sinopterus atavisms compared to Dsungaripterus to scale.

Figure 5. Sinopterus atavisms compared to Dsungaripterus to scale.

Sinopterus atavismus (Zhang et al. 2019; Early Cretaceous; IVPP V 23388) was originally considered a juvenile member of the Tapejaridae, but here nests as a small adult basal to Dsungaripteridae. The antorbital fenestra is not taller than the orbit. The carpals are not fused. No notarium is present. The antebrachium is robust. The distant pedal phalanges are longer than the proximal pedal phalanges. An internal egg appears to be present (but half-final-size adults were sexually mature according to Chinsamy et al. 2008,)

Sinopterus dongi IVPP V13363 (Wang and Zhou 2003) wingspan 1.2 m, 17 cm skull length, was linked to Tapejara upon its discovery, but is closer to Tupuxuara.

Sinopterus? liui (Meng 2015; IVPP 14188) is represented by a virtually complete and articulated specimen attributed to Sinopterus, but nests here at the base of Tupuxuara longicristatus.

Sinopterus jii (originally Huaxiapterus jii, Lü and Yuan 2005; GMN-03-11-001; Early Cretaceous) is basal to the Tapejara in the LPT, distinct from the other sinopterids basal to Tupuxuara.

Figure 5. Click to enlarge. The Tapejaridae arise from dsungaripterids and germanodactylids.

Figure 5. Click to enlarge. The Tapejaridae arise from dsungaripterids and germanodactylids.

The present LPT hypothesis of interrelationships
appears to be a novel due to taxon inclusion, reconstruction and phylogenetic analysis. If not novel, please let me know so I can promote the prior citation.

Traditional phylogenies falsely link azhdarchids with tapejarids
in an invalid clade ‘Azhdarchoidea‘. The LPT has never supported this clade (also see Peters 2007), which is based on one character: an antorbital fenestra taller than the orbit (that a few sinopterids lack). Pterosaur workers have been “Pulling a Larry Martin” by counting on this one character and by excluding pertinent taxa that would have shown them this is a convergent trait ever since the first cladograms appeared in Kellner 2003 and Unwin 2003.

Figure 1. Gene studies link swifts to hummingbirds. Trait studies link swifts to owlets. Trait studies link hummingbirds to stilts.

Figure x. Gene studies link swifts to hummingbirds. Trait studies link swifts to owlets. Trait studies link hummingbirds to stilts.

Unrelated update:
The stilt, Himantopus (Fig. x) has moved one node over and now nests closer to the hummingbird, Archilochus. Both arise from the Eocene bird, Eocypselus, which also gives rise to the hovering seagull, Chroicocephalus. The long, mud probing beak of the stilt was adapted to probing flowers in the hummingbird. All these taxa nested close together in the LRT earlier.


References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Kellner AWA 2003. 
Pterosaur phylogeny and comments on the evolutionary history of the group. Geological Society Special Publications 217: 105-137.
Lü J and Yuan C 2005. 
New tapejarid pterosaur from Western Liaoning, China. Acta Geologica Sinica. 79 (4): 453–458.
Maisano JA 2002. The potential utility of postnatal skeletal developmental patterns in squamate phylogenetics. Journal of Vertebrate Paleontology 22:82A.
Maisano JA 2002.
Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. Pp. 139-190. in Buffetaut, E. & Mazin, J.-M., (eds.) (2003). Evolution and Palaeobiology of Pterosaurs. Geological Society of London, Special Publications 217, London, 1-347.
Wang X and Zhou Z 2003. A new pterosaur (Pterodactyloidea, Tapejaridae) from the Early Cretaceous Jiufotang Formation of western Liaoning, China and its implications for biostratigraphy. Chinese Science Bulletin 48:16-23.
Zhang X, Jiang S, Cheng X and Wang X 2019. New material of Sinopterus (Pterosauria, Tapejaridae) from the Early Cretaceous Jehol Biota of China. Anais da Academia Brasileira de Ciencias 91(2):e20180756. DOI 10.1590/0001-3765201920180756.

wiki/Sinopterus

Growth pattern of a new large Romualdo pterosaur

Bantim et al. 2020 document
a new “pteranodontoid pterosaur with anhanguerid affinities (MPSC R 1935) from the Romualdo Formation (Lower Cretaceous, Aptian-Albian), is described here and provides one of the few cases where the ontogenetic stage is established by comparison of skeletal fusion and detailed osteohistological analyses.”

Figure 1. Excellent wing finger carpophalangeal joint from the Bantim et al. 2020 paper. Note the unfused sesamoid (extensor tendon process), a phylogenetic trait of lepidosaurs, not an ontogenetic trait of archosaurs, as phylogenetic analysis documents.

Figure 1. Excellent wing finger carpophalangeal joint from the Bantim et al. 2020 paper. Note the unfused sesamoid (extensor tendon process), a phylogenetic trait of lepidosaurs, not an ontogenetic trait of archosaurs, as phylogenetic analysis documents.

Continuing from the abstract
“The specimen … consists of a left forelimb, comprising an incomplete humerus, metacarpal IV, pteroid and digits I, II, III, IV, including unguals. This specimen has an estimated maximized wingspan of 7.6 meters, and despite its large dimensions, is considered as an ontogenetically immature individual. Where observable, all bone elements are unfused, such as the extensor tendon process of the first phalanx and the carpal series. The absence of some microstructures such as bone resorption cavities, endosteal lamellae, an external fundamental system (EFS), and growth marks support this interpretation. Potentially, this individual could have reached a gigantic wingspan, contributing to the hypothesis that such large flying reptiles might have been abundant during Aptian-Albian of what is now the northeastern portion of Brazil.”

Anhanguera

Figure 2. Anhanguera.

By comparison,
coeval Anhanguera has a 4.6m (15 ft) wingspan. The largest complete ornithocheirid, SMNK PAL 1136 has a 6.6m wingspan.

Bone elements fuse and lack fusion
in phylogenetic patterns (rather than ontogenetic patterns) in the clade Pterosauria, as documented earlier here in 2012. That is why you can’t keep pretending pterosaurs are archosaurs and not expect problems like this to accumulate. Your professors are taking your time and money and giving you invalidated information.

Figure 5. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136.

Figure 5. Largest Pteranodon to scale with largest ornithocheirid, SMNS PAL 1136.

It is a continuing black mark on the paleo community
that pterosaurs continue to be considered archosaurs by paid professionals when phylogenetic analysis (and Peters 2007 and the LRT) nests pterosaurs with lepidosaurs. That is why pterosaurs have lepidosaur phylogenetic fusion patterns (Maison 2002, 2002) distinct from archosaur ontogenetic fusion patterns. Just add taxa colleagues. The pterosaur puzzle piece does not fit into the archosaur slot… everyone admits that. The pterosaur puzzle piece continues to fit perfectly and wonderfully in the fenestrasaur tritosaur lepidosaur slot.


References
Bantim RAM et al. (5 co-authors) 2020. Osteohistology and growth pattern of a large pterosaur from the lower Cretaceous Romualdo formation of the Araripe basin, northeastern Brazil. Science Direct https://doi.org/10.1016/j.cretres.2020.104667
Maisano JA 2002. The potential utility of postnatal skeletal developmental patterns in squamate phylogenetics. Journal of Vertebrate Paleontology 22:82A.
Maisano JA 2002.
Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Peters D 2007. 
The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.

https://pterosaurheresies.wordpress.com/2013/05/14/phylogenetic-fusion-patterns-in-pterosaurs/

A juvenile Eusthenopteron enters the LRT

Fish expert, John Long 1995 (p. 209) wrote:
The juvenile skull of a crossopterygian fish, Eusthenopteron (Figs. 1,3) has more features in common with that of an early amphibian Crassigyrinus (Fig. 4), that it’s adult skull would have had.”

Long goes on to explain about paedomorphosis and heterochrony during the transition from fish to tetrapod.

Euthenopteron was a good transitional taxon several years ago. Recently it was replaced in the LRT by a flatter taxon, Cabonnichthys.

Figure 1. Eusthenopteron juvenile in situ from Schultze 1984. Large plate ventral to the mandible overlaps a convex ventral margin. The quadratojugal is not labeled here. Several bones are re-labeled here.

Figure 1. Eusthenopteron juvenile in situ from Schultze 1984. Large plate ventral to the mandible overlaps a convex ventral margin. The quadratojugal is not labeled here. Several bones are re-labeled here.

Let’s put Long’s 1995 statement to the test
by adding Eusthenopteron ‘junior’ (Schultze 1984) to the large reptile tree (LRT, 1698+ taxa; subset Fig. 5).

Results: The juvenile nested with the adult Eusthenopteron in the LRT, falsifying Long’s statement.
Note: Several bones are relabeled here vs. Schultze’s original designations.

Worthy of note:
The juvenile Eusthenopteron shares several traits with another, often overlooked, small taxon with similar large eyes, Koilops, which nests at the base of a nearby derived node in the LRT (Fig. 5). Based on phylogenetic bracketing, Koilops is also a juvenile. All sister taxa are larger and without juvenile proportions.

Figure 2. Koilops is a flat-headed sister to Spathicephalus, but with teeth, larger orbits and a shorter snout

Figure 2. Koilops is a flat-headed smaller sister to Elpistostege, but with larger teeth, larger orbits and a shorter snout. These traits indicate Koilops is a juvenile.

So Long’s point about paedomorphosis and heterochrony
was  not correct in this case. His ‘matching tetrapod’, Crassigyrinus (Fig. 4), nests several nodes apart from pre-tetrapods in the LRT (off the subset chart in Fig. 5).

Koilops post-crania remains unknown,
but it nests at the base of Elpistostege, Tiktaalik and Spathicepahlus on one branch, Panderichthys + Tetrapoda on the other. So Koilops likely had lobe fins and a straight tail. Perhaps Koilops was a juvenile elpistostegid ready to mature into something larger, with smaller eyes, more like Elpistostege.

Figure 2. Juvenile and adult Eusthenopteron compared from Schultze 1984. The cranium of the juvenile appears convex here, but was likely flatter.

Figure 3. Juvenile and adult Eusthenopteron compared from Schultze 1984. The cranium of the juvenile appears convex here, but was likely flatter based on figure 1.

From the Schultze 1984 abstract:
A size series of thirty-five specimens of Eusthenopteron foordi Whiteaves, 1881 , shows isometric and allometric changes. As in Recent fishes, the main difference between small (juvenile) and large (adult) specimens is the relative size of the orbit and of the head. With the exception of the caudal prolongation, all fin positions remain isometric to standard length.”

Figure 5. Crassigyrinus has little to no neck.

Figure 4. Crassigyrinus has little to no neck.

Contra Long 1995 and all prior basal tetrapod workers, the LRT indicates the transition from fish to tetrapod occurred among flat-head taxa, like Trypanognathus.  Crassigyrinus Fig. 4) is a distinctly different stegocephalid with a taller skull, more like those of the more famous traditional transitional taxa, Ichthyostega and Acanthostega. The new fish-to-tetrapod transitional taxa were recovered by simply adding taxa overlooked by prior workers. Taxon exclusion continues to be the number one problem with vertebrate paleontology today, according to results recovered by the LRT. This free, online resource minimizes taxon exclusion.

Figure x. Subset of the LRT, focusing on fish for July 2020.

Figure x. Subset of the LRT, focusing on fish for July 2020.

Not sure if fish expert John Long
would make the same statement today. Let’s hope things have changed in the last 25 years of vertebrate paleontology.


References
Long JA 1995. The Rise of Fishes. The Johns Hopkins University Press, Baltimore and London 223 pp.
Schultze H-P 1984. Juvenile specimens of Eusthenopteron foordi Whiteaves, 1881 (Osteolepiform Rhipidistian, Pisces) from the Late Devonian of Miguasha, Quebec, Canada. Journal of Vertebrate Paleontology 4(1):1–16.

wiki/Eusthenopteron

Maybe Paraceratherium is really a giant horse.

Figure 1. Subset of the large reptile tree focusing on horses and their kin.

Figure 1. Subset of the large reptile tree focusing on ungulates and their kin.

Today’s heresy began when several ungulate taxa
were added to the large reptile tree (LRT, Fig. 1, now 907 taxa, completely resolved with 228 traits). Equus, the horse; Paraceratherium, the giant hornless ‘rhino’; Ceratotherium the white rhinoceros and Embolotherium, a  Mongolian brontothere.

It is widely accepted
and supported by the LRT that horses and rhinos share a common ancestor (Fig. 1). In this case, the LRT recovered either 1) an overlooked relationship, or 2) a case of convergence between Paraceratherium and Equus (Fig. 2). Wikipedia  notes that rhinos are more closely related to tapirs. In the LRT tapirs are basal to a sister clade to the rhino/horse clade. Hyracotherium and Heptodon are basal to the rhino/horse clade.

Figure 1. Equus and Paraceratherium nest together on the LRT.

Figure 2. Equus and Paraceratherium currently nest together on the LRT. Additional taxa will, no doubt, change that, but at present, Paraceratherium shares more traits with Equus than Ceratotherium, the white rhino (Fig. 2). The long neck and premaxillay teeth, along with other traits, separate these two from extant rhinos.

Equus ferus (Linneaus 1758; Figs. 2,3) includes several extant horses, mules and zebras. Compared to Hyracotherium the Equus preorbital region is longer, the frontal produces a postorbital bar that contacts the squamosal. The premolars are molarized. All four limbs end in a single toe, digit 3.

Figure 1. Equus the extant horse.

Figure 3. Equus the extant horse has a postorbital bar, an elongate rostrum and a single toe on each limb.

Hyracotherium leporinum (Owen 1841; 78 cm long; Eocene, 55-45 mya; BMNH C21361nests basal to the horse/rhino clade, EquusHeptodon (Fig. 5) is an Eocene sister. Canines remained. A diastema separated the canine from the premolars. The manus has four hoofed toes. The pes has three hoofed toes. The premolars were becoming molarized. Compare the skull of dog-size Hyracotherium to the similar skull of Paraceratherium, one of the largest land mammals of all time and Equus, the horse.

Figure 2. Hyracotherium is an Eocene horse sister in the LRT. Skull bones are colorized here.

Figure 4. Hyracotherium is an Eocene horse sister in the LRT. Skull bones are colorized here.

Heptodon (Pachynolophus) posticus (Cope 1882; Eocene, 50 mya; 1m in length) was derived from a sister to Tapirus and was itself a sister to Hyracotherium and the base of brototheres like Embolotherium (below). Heptadon had reduced canines and developed a diastema (lack of teeth) posterior to them. The posterior cranium was slightly elevated. The manus had four digits. The pes had three. 

Figure 4. Heptodon originally nested with Tapirus, but with the addition of Equus, Hyracotherium and Embolotherium it shifted to nest with Embolotherium.

Figure 5. Heptodon earlier nested with Tapirus, but with the addition of Equus, Hyracotherium, Paraceratherium and Embolotherium it nested closer to them.

The extant white rhinoceros
Ceratotherium simus (extant, Figs. 6, 7)) shares little in common with Paraceratherium, but shares a long list of traits with Embolotherium, including an oddly elevated pair of nasals and the near complete loss of the lumbar region. Both had smaller ancestors, so direct comparisons yield several possible convergences that currently nest as homologs. That’s what happens with taxon exclusion.

Figure 6. Ceratotherium, simum, the white rhinoceros with keratinous horns in dark brown. Note the elevated nasals and convex dentary ventral margin.

Figure 6. Ceratotherium, simum, the white rhinoceros with keratinous horns in dark brown. Note the elevated nasals and convex dentary ventral margin.

Figure 7. Ceratotherium (white rhino) skeleton, distinct from the long-legged Paraceratherium.

Figure 7. Ceratotherium (white rhino) skeleton, distinct from the long-legged Paraceratherium.

The last taxon to be added is
Embolotherium andrewsi (Osborn 1929; Late Eocene; 2.5m tall at the shoulder; Mongolia; Figs. 4, 5). It nests as a sister to the rhino, Ceratotherium, but this is likely to be overturned on convergence when additional taxa are added. This highly derived brontothere (= titanothere) has forked ‘horns’ (= rams). The rams are elevated nasal bones, hollow and fragile. These are in contrast to the solid rams of North American brontotheres. Click here to see the original AMNH illustration of the Embolotherium skull that portrays the area beneath the elevated nasal as a thick fleshy area. Alternatively Wikipedia reports, “the bony nasal cavity extends to the peak of the ram, thus implying that the nasal chamber was greatly elevated, possibly creating a resonating chamber.”

Figure 2. Brontotherium, a sister to Embolotherium.

Figure 8. Brontotherium, a sister to Embolotherium, which is known from skulls, but no complete post-crania.

The skull of Embolotherium was 2x wider than tall at the orbits. The molars were much larger than the premolars, which were themselves molarized. The canines were vestiges. The posterior skull was greatly elevated. The dorsal spines were greatly elevated (Fig. 4). The lumbar region was reduced. The ilia were transverse. Four fingers are retained by the manus, indicating an early divergence from three-fingered horses and rhinos.

Figure 4. Embolotherium andrewsi modified from the AMNH website to show a possible inflatable narial area.

Figure 9. Embolotherium andrewsi animation modified from the AMNH website (see link above) to show a possible inflatable narial area, contra the original restoration with a fleshy, immobile sub-nasal area.

Figure 8. Paraceratherium pes. Note the reduced lateral and medial toes (2 and 4). As in Equus, and distinct from Ceratotherium, the central toe is much larger.

Figure 10. Paraceratherium pes. Note the reduced lateral and medial toes (2 and 4). As in Equus, and distinct from Ceratotherium, the central toe is much larger.

These are all perissodactyls
(odd-toed ungulates)
despite the fact that the manus has four digits. The pes (with toes) has an odd-number of digits (three or one). Wikipedia nests Desmostylia and Anthracobunidae among the perissodactyls, but they nest with hippos and mesonychids in the LRT.

Hyracodon
is not included here, but nests in the LRT between Hyracotherium and Heptodon, far from Paraceratherium. Apparently Equus and Paraceratherium have not been tested together in phylogenetic analysis under the assumption that one was a horse and the other a rhino.

Finally
note the large third digit of the pes of the giant three-toed horse, Paraceratherium (Fig. 10), as in Equus and distinct from Ceratotherium, which has three toes, but sub equal in size.

The above was dashed off
a little more quickly than usual. Please bring to my attention any typos or dangling hypotheses.

 

References
Cope ED 1882. Paleontological Bulletin 34:187.
Froehlich DJ 2002. Quo vadis eohippus? The systematics and taxonomy of the early Eocene equids (Perissodactyla). Zoological Journal of the Linnean Society. 134 (2): 141–256.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
Osborn HF 1929. Embolotherium, gen. nov., of the Ulan Gochu, Mongolia. American Museum novitates; no. 353.
Owen R 1841. Description of the Fossil Remains of a Mammal (Hyracotherium leporinum) and of a Bird (Lithornis vulturinus) from the London Clay. Transactions of the Geological Society of London, Series 2, VI: 203-208.

wiki/Equus
wiki/Hyracotherium
wiki/Embolotherium
wiki/Paraceratherium
wiki/Heptodon

Pterodaustro isometric growth series

Tradtional paleontologists think pterosaur babies had a cute short rostrum that became longer with maturity and a large orbit that became smaller with maturity (Fig. 1). This is a growth pattern seen in the more familiar birds, crocs and mammals.

Pterodaustro embryo as falsely imagined in Witton 2013. The actual embryo had a small cranium, small eyes and a very long rostrum.

Figure 1. Pterodaustro embryo as falsely imagined in Witton 2013. The actual embryo had a small cranium, small eyes and a very long rostrum.

Unfortunately
these paleontologists ignore the fossil evidence (Figs 2, 3). These are the data deniers. They see things their own way, no matter what the evidence is. The data from several pterosaur growth series indicates that hatchlings had adult proportions in the skull and post-crania. We’ve seen that earlier with Zhejiangopterus (Fig. 2), Tapejara, Pteranodon, Rhamphorhynchus and others. Still traditional paleontologists ignore this evidence as they continue to insist that small short rostrum pterosaurs are babies of larger long rostrum pterosaurs.

Figure 1. Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

Figure 2 Click to enlarge. There are several specimens of Zhejiangopterus. The two pictured in figure 2 are the two smallest above at left. Also shown is a hypothetical hatchling, 1/8 the size of the largest specimen.

As readers know,
several pterosaur clades went through a phase of phylogenetic miniaturization, then these small pterosaurs became ancestors for larger clades. Pterosaurs are lepidosaurs and they grow like lepidosaurs do, not like archosaurs do.

Today we’ll look at
the growth series of Pterodaustro (Fig. 1), previously known to yours truly only from adults and embryos. Today we can fill the gaps with some juveniles.

This blog post is meant to help traditional paleontologists get out of their funk.

A recent paper
on the braincase of odd South American Early Cretaceous pterosaur Pterodaustro (Codorniú et al. 2015) pictured three relatively complete skulls from a nesting site (Fig. 1). I scaled the images according to the scale bars then added other available specimens.

Figure 1. Pterodaustro skulls demonstrating an isometric growth series. One juvenile is scaled to the adult length. One adult is scaled to the embryo skull length. There is no short rostrum and large orbit in the younger specimens.

Figure 1. Pterodaustro skulls demonstrating an isometric growth series. One juvenile is scaled to the adult length. One adult is scaled to the embryo skull length. There is no short rostrum and large orbit in the younger specimens. If you can see differences in juvenile skulls vs. adult skulls, please let me know. All these specimens come from the same bone bed.

You can’t tell which skulls are adults or juveniles
without scale bars and/or comparable specimens. As we established earlier, embryos are generally one-eighth (12.5%) the size of the adult. Pterodaustro follows this pattern precisely.  We have adults and 1/8 size embryos and several juveniles of intermediate size.

No DGS was employed in this study.

If you know any traditional paleontologists, 
remind them that the data indicates that pterosaurs matured isometrically, like other  lepidosaurs. Those small, short rostrum specimens, principally from the Late Jurassic Solnhofen Formation, are small adults, transitional from larger ancestors to larger descendants. Tiny pterosaurs experiencing phylogenetic miniaturization(as in birds, mammals, crocs, turtles, basal reptiles, and many other clades) that helped their lineage survive while larger forms perished, Sadly, no tiny pterosaurs are known from the Late Cretaceous when they all became extinct.

References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Codorniú L, Paulina-Carabajal A and Gianechini FA 2015.
 Braincase anatomy of Pterodaustro guinazui, pterodactyloid pterosaur from the Lower Cretaceous of Argentina. Journal of Vertebrate Paleontology, DOI:10.1080/02724634.2015.1031340

The origin of feathers and hair (part 2: hair)

Yesterday we looked at reptile skin and scales, alpha and beta-keratins and examined the fossil record of scales, naked skin and pterosaur extra dermal membranes. Today we’ll take on mammal hair.

Pre-mammals
Mammals, like Megazostrodon, evolved in the Jurassic from synapsid reptiles, like Archaeothyris, that first appeared in the Late Pennsylvanian.

Dhouailly 2009 reports: “The synapsid lineage, which separated from the amniote taxa in the Pennsylvanian about 310 million years ago, may have evolved a glandular rather than a scaled integument, with a thin alpha-keratinized layer adorned with alpha-keratinized bumps. Those bumps may have even presented some cysteine-rich alpha-keratins, precursors of the hair-type keratins. In addition, the first synapsids may have developed both a lipid barrier outside the epidermis, similar to current amphibians living in xeric habitats, and some lipid complex with the alpha-keratins of the stratum corneum as in current mammals as a means to strengthen the barrier against water loss of the integument.”

So reptilian scales were never part of the mammal legacy — just naked glandular skin.

Mammals
A dense coat of fur is found in all basal extant mammals, even those that lay eggs. Thus the origin of hair is to be found in the common ancestor of all living mammals, perhaps among therapsid-grade synapsids (Thrinaxodon Chiniquodon), or, more conservatively, perhaps right at the origin of early Jurassic mammals.

Dhouailly 2009 reports: “No intermediate form has ever been found between scales and hairs, resulting in only a few proposals of how mammalian hairs may have evolved from scales. These proposals were based on the development of sensory bristles in the hinge scale region of reptiles.”  Unfortunately basal reptiles and therapsids did not have scales (see below).

The traditional cynodont whisker hypothsis
Foramina (tiny holes) on the faces of basal gorgonopsians, therocephalians and cynodonts have been interpreted as providing passages for nerves and blood vessels supplying movable skin (subcutaneous muscles) and sensory vibrissae (whiskers). This would represent the first appearance of hair only to be followed by more and more hair spreading around the body. This essentially duplicates the new hypothesis on feather origin by Persons and Currie (2015, see that discussion tomorrow).

Unfortunately for this hypothesis,
the basal lizard, Tupinambis has similar rostral foramina, yet it lacks sensory vibrissae (Bennett and Ruben 1986).

An alternate mammal hair genesis hypothesis
Given that pelycosaurs and Estemmenosuchus were naked and had no hair, the origin of mammal-type hair must have occurred closer to mammals. On their way to evolving into mammals, taxa like Pachygenelus and Megazostrodon became progressively smaller in a rather common process known as phylogenetic miniaturization (the opposite of Cope’s Rule).

Due to their increased surface/volume ratio, smaller animals find it more difficult to internally thermoregulate because their insides are closer to their outsides. Having insulating fur when tiny would be helpful. That’s the traditional hypothesis for mammal hair genesis in tiny taxa, like Megazostrodon. Unfortunately the insulation hypothesis gives no reason for the first appearance of tiny sprigs of precursor hair, not yet plentiful enough to trap air (for insulation). Nor does it take into account that the smallest of all basal mammals, their newborns, are hairless.

Dhouailly 2009 reports: “Hairs [may have] evolved from sebaceous glands, with the hairshaft serving as a wick to draw the product of the gland to the skin surface, strengthening the barrier against water loss.”

Figure 2. An automobile driver can sense the presence of the curb on approach when a curb feeler is in place. This saves wear and tear on tires, just like individual hairs would touch the inside of burrows before the skin comes into contact.

Figure 2. An automobile driver can sense the presence of a curb on approach when a “curb feeler” is in place. This saves wear and tear on tires. Similarly individual hairs would touch the inside of burrows before the skin comes into contact.

The curb-feeler hypothesis
As others have noted, individual hairs provide tactile feedback. Those are especially useful to nocturnal and burrowing animals.

Naked mole rats provide a good analogy. Like therapsids, naked mole rats burrow, adjust their internal temperature to ambient temperatures, AND they have only a few whisker-like hairs that crisscross the body to form a sensitive array that helps them navigate in the dark. We know that certain small cynodonts were  also burrowers. That’s where we find them. We don’t know if they had whisker-like hairs that crisscrossed their body. Only the bones are preserved.

In this way,
individual hairs would have been like curb-feelers (Fig. 2), small wires that make a noise whenever a 1950s era automobile approaches a curb. Thus provided, basal mammals could have avoided multiple abrasions while running through their tunnels using their own curb feelers.

Nevertheless,
if that’s how hair started, once provided with the ability to grow hair, simply growing more hair would have provided incremental opportunities to spend more and more time outside of the burrow. Hair insulated mammals not only from ambient temperature, but from the environment at large, including the approach of winged insects like flies and mosquitoes. Note that those insects that finally developed the ability to burrow past the hair barrier, fleas, lost their wings in order to do so.

Navigation skills
learned in dark tunnels could be readily transferred to leaf litter in the open air at night (all the while avoiding the predatory gaze of hungry Jurassic dinosaurs).

Opossum tail showing rectangular eupelycosaurian scales

Figure 2. Opossum tail showing false scales. A couple of ‘curb feelers’ appear on the proximal tail.

The “scaly tail” of mammals,
like the opossum (Fig. 2), is actually, a criss-cross series of epidermal folds interspersed with hairs, not homologous with the scale of any other animal (Dhouailly 2009).

Figure 3. Naked mouse babies surround the furry mother mouse.

Figure 3. Naked mouse babies surround the furry mother mouse. The babies may be recapitulating evolution as they are naked and unable to maintain their own body temperature without a little help from mom.

The surprising origin of mammary glands
Dhouailly 2009 reports: “The mammary gland apparently derives from an ancestral sweat or sebaceous gland that was associated with hair follicles, an association which is retained in living monotremes, and transiently in living marsupials. The original function of the mammary gland precursor may not have been feeding the young, but as a means to provide moisture to the eggs.”

Tomorrow: dinosaur feathers.

References
Bennett AF and Ruben JA 1986. The metabolic thermoregulartory status of therapsids. In The Ecology and Biology of Mammal-like reptiles (Hottom, Roth and Roth eds) 207-218. Smithsonian Institution Press, Washington DC
Chudinov PK 1970. Skin covering of therapsids [in Russian] In: Data on the evolution of terrestrial vertebrates (Flerov ed.) pp.45-50 Moscow: Nauka.
Dhouailly D 2009. A new scenario for the evolutionary origin of hair, feather, and avian scales. Journal of Anatomy 214:587-606.
Persons WC4 and Currie PF 2015. Bristles before down: A new perspective on the functional origin of feathers.Evolution (advance online publication) DOI: 10.1111/evo.12634

 

Ontogenetic crest development in Tupuxuara

Let’s set the stage
Earlier we looked at the isometric growth of the azhdarchid pterosaur, Zhejiangopterus and the juvenile Pteranodon. Earlier we falsified unsupported claims that tiny Solnhofen pterosaurs were allometric juveniles of larger forms. Earlier we reported on four pterosaur embryos that demonstrated isometric growth. None had the larger eyes and shorter rostrum that typify hatchling and newborn mammals, birds and crocs (contra Bennett 2006). Even so, Witton 2013 continues to promote the false hypothesis of allometric growth during ontogeny in pterosaurs (Fig. 1).

But we haven’t yet touched on the crest size question
Today we’ll show evidence that yes, crest size does increase during ontogeny. And, really, how else would you ever expect to get such big crests inside an eggshell? However, rostrum length and eye size does not change during ontogeny, no matter how much Bennett and Witton want that to happen. Witton unwittingly demonstrates this himself with a juvenile Tupuxuara (Fig. 1).

Figure 2. Witton 2013 promotes the myth that small Rhamphorhynchus specimens were juveniles of larger specimens. Actually the small ones were ancestral to the larger ones as recovered in phylogenetic analysis.  Below: An actual juvenile Tupuxuara, matched to another species of Tupuxuara with a longer rostrum. Note the juvenile eyes are not large. Crest size does increase with ontogenetic age.

Figure 1. Witton 2013 promotes the myth that small Rhamphorhynchus specimens were juveniles of larger specimens. Actually the small ones were ancestral to the larger ones as recovered in phylogenetic analysis.
Below: An actual juvenile Tupuxuara, matched to another species of Tupuxuara with a longer rostrum. See figure 3 for a better match to an adult. Note the juvenile eyes are not large. Crest size does increase with ontogenetic age.

Today
we have three size of Tupuxuara (Fig. 2) based on the Goshura specimen including two likely juveniles morphologically close to it. Each has a distinct skull showing some variation, but together they shed some light on crest development with maturation in these large Cretaceous pterosaurs. Note that none have the traditional short rostrum and large eyes Bennett (2006) predicted. Neither the juveniles nor the adult have the long rostrum of the Tupuxuara longicristatus specimen that Witton (2013) substituted (Fig. 1) for an adult version of this species. Note that the middle colorized specimen has a relatively longer rostrum than the Goshura specimen. This may represent individual variation grading into speciation.

Figure 1. Ontogenetic skull and crest development in Tupuxuara. Note the eyes are small and the rostrum is long in juveniles. Only the crest expands and only posteriorly.

Figure 2. Ontogenetic skull and crest development in Tupuxuara. Note the eyes are small and the rostrum is long in juveniles and adults, even longer in the middle juvenile. Only the crest expands  posteriorly.

TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It's a close match to that of Tupuxuara, otherwise known only from Early Cretaceous South American strata.

Figure 3. TMM 42489-2, the tall crested Latest Cretaceous large rostrum and mandible. It’s a close match to that of Tupuxuara longicristatus, otherwise known only from Early Cretaceous South American strata. Note the big difference in rostral length is a phylogenetic difference, not an ontogenetic one. If you were hell bent on proving allometric growth, this is the skull I would use, like the one Witton did. 

We also have a juvenile Tapejara with a crest
And the crest not much smaller than an adult crest. Skull proportions are virtually the same between adult and juvenile. And yet, look, there’s another long rostrum adult, just another variation on a theme.

Figure 4. Juvenile Tapejara with two adults of distinct species. Note the rather large crests on the juvenile, but otherwise the skull had adult proportions.

Figure 4. Juvenile Tapejara with two adults of distinct species. Note the rather large crests on the juvenile, but otherwise the skull had adult proportions.

Along the same lines:
Witton 2013 also attempted to promote the Bennett (1995) idea that small Rhamphorhynchus specimens were actually juveniles (Fig. 1). Neither worker used phylogenetic analysis which demonstrates that known small Rhamphorhychus specimens were actually primitive, closer to the outgroup taxon, Campylognathoides.

You’ll recall
Bennett (1991, 2000) said that short-crested, smaller specimens of Pteranodon represented juveniles and females. That was falsified using phylogenetic analysis that recovered short-crested Pteranodon specimens closer to short-crested outgroup taxa, such as Germanodactylus. We do know of Ptweety, the juvenile Pteranodon, but it had a long rostrum and, unfortunately, the crest was broken off

Nevertheless, it’s obvious that long and tall-crested pterosaur specimens could not have fit such long and tall crests into an eggshell. So there must have been some sort of crest growth during ontogeny in large crested specimens. And this, so far, is the evidence for it.

References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153
Bennett SC 2006. Juvenile specimens of the pterosaur Germanodactylus cristatus, with a review of the genus. Journal of Vertebrate Paleontology 26:872–878.SMNS
Witton M. 2013. Pterosaurs. Princeton University Press. 291 pages.

Getting Big and Getting Small, a NEXT Page from Nat Geo

The most recent issue of Nat Geo included a one page note called, “Sizing Up.”

Nat Geo reporter Gretchen Parker sourced Allistair Evans, of Monash U, Australia, who noted “It takes a minimum of 3 million generations for a dolphin-sized aquatic mammal to increase to the size of a blue whale.” 1000x change in size, graphics impressive.

“It takes 1.6 million generations for a sheep-size land mammal to increase to the size of an elephant.” 100x change in size

“But it takes only a minimum of 0.1 million generations for an elephant-sized land mammals to decrease to the size of a sheep. 100x change in size.

“5 million generations” to go from rabbit-sized to elephant-size. 1000x

“24 million generations” to go from mouse-size to elephant-size. 100,000x

All this is interesting, but more interesting to PterosaurHeresies readers might be some similar hypotheses regarding prehistoric reptiles, particularly pterosaurs.

Pterodaustro embryo

Figure 1. Pterodaustro embryo. At one-eighth the size of a large adult, this embryo retains most of the proportions of the adult, including a long rostrum and tiny eye.

Chinsamy et al. (2008) noted that in Pterodaustro, the only pterosaur for which we have a complete growth series, half grown specimens appear to be sexually mature. At half size, the pelvis is also half size, able to pass eggs of half size producing hatchlings of half size, more or less. In three generations such a progression could lead to a one-eighth size adult, which would be the size of a hatchling of the original Pterodaustro. Now I’m not saying this is exactly how size reduction happened in pterosaurs. The three generations is just the ‘speed limit’ for getting small, something pterosaurs did over and over again, producing new clades following these many size decreases as size thereafter increased.

Some pterosaurs, like Quetzalcoatlus, became very large and very famous. Other pterosaurs became very small. They’re not famous. They don’t even rate a distinct genus, having been relegated to the trash heap with the label, “juvenile.” They are excluded from phylogenetic analysis  and unjustly so. They are important.

Of course getting big again simply depends on creating eggs later in life when the mother is slightly surpassing the 8x growth pattern having a larger pelvis to pass a larger egg. Like elephants, getting bigger probably took more time than getting smaller.

Overall size does affect morphology and evolution. Early and late maturation affects the next generation. Hormones count! Hormones also drive secondary sexual characteristics, like frills and crests. These things add up, or subtract out, over many generations.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.

Mesosaurus Embryos!

Good friend, Dr. Graciela Piñeiro et al. (2012) just described the oldest known amniotic embryos. They belong to mesosaurs (Gervais 1865). From their abstract: “The earliest undisputed crown-group amniotes date back to the Late Carboniferous, but the fossil record of amniotic eggs and embryos is very sparse, with the oldest described examples being from the Triassic. Here, we report exceptional, well preserved amniotic mesosaur embryos from the Early Permian of Uruguay and Brazil. These embryos provide the earliest direct evidence of reproductive biology in Paleozoic amniotes. The absence of a recognisable eggshell and the occurrence of a partially articulated, but well-preserved embryo within an adult individual suggest that mesosaurs were viviparous or that they laid eggs in advanced stages of development. Our finds represent the only known documentation of amniotic embryos in the Paleozoic and the earliest known case of viviparity, thus extending the record of these reproductive strategies by 90 and 60 Ma, respectively.”

Embryo Mesosaurus

Figure 1. Embryo Mesosaurus curled up within its ellipsoid amniotic membrane, but no egg shell was preserved. Left: specimen; Middle: tracing of specimen; Right: restoration of specimen.

The embryo was ~10% the size of an average adult and coiled as if in an ellipsoid egg. The snout was relatively short. The head was relatively large. Despite the elliptical shape of the embryos, no shell was preserved. Some embryos were found within their mother. Only one and rarely two were carried at a time. These data support the large reptile family tree that recovered a mesosaur/thalattosaur/ichthyosaur relationship in which ichthyosaurs are known to exhibit live birth (viviparity) emerging from their amniotic sac prior to birth.

Lizards typically carry the embryo within the uterus for extended periods. Many exhibit viviparity, but lizards and mesosaurs are not related.

Ichthyosaurs and sauropterygians also exhibit viviparity and are closer to mesosaurs. All three are distantly related to both therapsids (basal mammals lay eggs) and archosaurs (both birds and crocs lay eggs). So viviparity in this clade seems to have had its genesis in mesosaurs.

There’s more big news on mesosaurs to come.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Gervais P 1865. Du Mesosaurus tenuidens, reptile fossile de l’Afrique australe. Comptes Rendus de l’Académie de Sciences 60:950–955.
Piñeiro G, Ferigolo J, Meneghel M and Laurin M 2012. The oldest known amniotic embryos suggest viviparity in mesosaurs. Historical Biology: An International Journal of Paleobiology, DOI:10.1080/08912963.2012.662230

Basic Problems with “Life History of Rhamphorhynchus Inferred from Bone Histology…”

Today’s paper on Rhamphorhynchus bone histology (Prondvai et al. 2012) reported, “Whereas morphological studies suggested a slow crocodile-like growth strategy and superprecocial volant hatchlings, the only histological study hitherto conducted on Rhamphorhynchus concluded a relatively high growth rate for the genus. These controversial conclusions can be tested by a bone histological survey of an ontogenetic series of Rhamphorhynchus.”

The family tree of the Rhamphorhynchus.

Figure 1. Click to enlarge. The family tree of Rhamphorhynchus in phylogenetic order. Note only the very largest specimen was large enough to produce a hatchling the size of the smallest specimen based on an 8:1 ratio of adult to hatchling as in Pterodaustro and based on egg size/pelvic opening. If so, that means ALL the other Rhamphorhynchus specimens were juveniles despite their many morphological differences. No, this was a clade with a variety of morphologies and sizes, a fact overlooked by the Prondvai et al. (2012) study.

Rhamphorhynchus presents a wide variety of adult sizes with the largest specimens 8x as tall as the smallest (Fig. 1). Unfortunately, the authors gave no indication that the five specimens in their study were from the same single species (of several) within the genus which would have presented an ontogenetic series. This can be determined only by a cladistic analysis of several dozen Rhamphorhynchus specimens, including their five study specimens, but that first step was not done.  Figure 1 demonstrates a phylogenetic series (as determined by cladistic analysis) of the genus Rhamporhynchus. The morphological differences are easy to see. Even the pedal phalanges differ among species (Peters 2009), as noted earlier.

A selection of Rhamphorhynchus feet

Figure 2. A selection of Rhamphorhynchus feet compared to the new one associated with a large fish. Note the morphological differences exhibited by the new specimen, WDC CSG 255 (far right).

 

Furthermore
Substantial morphological change during growth does NOT occur in pterosaurs, as already demonstrated by embryos (especially Pterodaustro). What we’re looking for are tiny versions of the adults already known in the fossil record, and to my knowledge, no juveniles have yet been found that morphologically match 2x to 8x larger adults (the latter being the standard difference between hatchlings and adults as determined by hypothetical egg sizes matched to pelvic openings and the example of Pterodaustro). Ptweety is the only juvenile pterosaur I know of and it also has the proportions of an adult.

What Happens During a Phylogenetic Size Squeeze in Pterosaurs?
“Teens” start having babies. Sexual maturity comes sooner and sooner. Longevity decreases. Adult size decreases. Chinsamy et al. (2008) reported that sexual maturity in Pterodaustro occurred at half the largest size attained. Smaller hips produce smaller eggs. The bone histology of a small specimen with a shorter lifespan mimics the expected histology of a juvenile. Scapulocoracoid fusion likewise disappears during serial phylogenetic size reductions.

Superprecocial Flight
The limiting factor in superprecocial flight still appears to be dermal evaporation and desiccation due to a large surface of volume ratio in tiny pterosaurs. Only those pterosaurs hatching from eggs the size of the three published embryos appear to create a threshold size for flight shortly after hatching. Smaller hatchlings than this had to be terrestrial, hiding in damp leaf litter, rather than taking to the skies, so the lack of flying in hatchling pterosaurs reported by Prondvai et al. (2012) is likely correct, though not for the same reason.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Prondvai E, Stein K, Ősi A. and Sander MP (2012)
 Life History of Rhamphorhynchus Inferred from Bone Histology and the Diversity of Pterosaurian Growth Strategies.
PLoS ONE 7(2): e31392. doi:10.1371/journal.pone.0031392
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031392