Was the AMNH Tanytrachelos ‘with child’?

Tanytrachelos ahynis (Olsen 1979, holotype AMNH 7496; holotype Fig. 1) Latest Triassic, 200 mya, was derived from Macrocnemus and was a sister to Langobardisaurus and Tanystropheus. All are tritosaur lepidosaurs in the lineage of the terrestrial ancestors of pterosaurs, the Fenestrasauria… all ultimately derived from an earlier sister to late-surviving Huehuecuetzpalli and Tijubina.

Figure 1. AMNH 7496 holotype of Tanytrachelos with original tracing from Olsen 1979. DGS colors added.

Figure 1. AMNH 7496 holotype of Tanytrachelos with original tracing from Olsen 1979. DGS colors added.

The AMNH specimen
(Fig. 1) preserved in ventral exposure, appears to have two halves of a leathery eggshell and an ‘exploded’ embryo, best described as several dozen tiny bones that should not be there, unless, perhaps this was a gravid adult… or something else, like gastroliths, undigested prey… hard to tell. In any case, some of the pectoral bones also have new identities here.

Figure 5. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo.

Figure 2. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo. These are the sorts and sizes of bones one should look for in any maternal Tanytrachelos.

Figure 1. Tanytrachelos hopping to match Gwyneddichnium tracks (see figure 2).

Figure 3. Tanytrachelos hopping to match Gwyneddichnium tracks (see figure 2).

Distinct from Langobardisaurus,
Tanytrachelos has twelve cervicals, but none were gracile. The posterior cervical ribs had large heads that kept the rods far from each centrum. Heterotopic bones were present. These appear to be elongated chevrons, as in Tanystropheus. Rare hopping prints (Fig. 2) match the size and shape of Tanytrachelos pedes.

langobardisaurus-pectoral-girdle

Figure 4. The sternal complex of several other tritosaurs. Tanytrachelos is closer to Tanystropheus, not quite like any of these related taxa, but all are informative.

The elliptical sternum
of Tanytrachelos was wide, as in Langobardisaurus (Fig. 3), but the clavicle remained gracile, as in Huehuecuetzpalli (Fig. 3). The humerus was slightly bowed. Metacarpal I aligned with the others. Metatarsal III was the longest. Digit III was the longest as in Langobardisaurus tonelloi.


References
Olsen PE 1979. A new aquatic eosuchian from the Newark Supergroup Late Triassic-Early Jurassic) of North Carolina and Virginia. Postilla 176: 1-14.
Smith AC 2011. Description of Tanytrachelos ahynis and its implications for the phylogeny of Protorosauria. PhD dissertation. Virginia Polytechnic Institute and State University.

 

One more trait linking hippos to mysticetes (baleen whales)

Vibrassae
are sensory organs found in hippos and baleen whales. Odontocete whales lack such vibrissae.

Figure 1. Mysticete (right whale) vibrissae compared to hippo vibrissae. Odontocete whales lack such structures.

Figure 1. Mysticete (right whale) vibrissae compared to hippo vibrissae. Odontocete whales lack such structures.

Earlier the large reptile tree (LRT, 1644+ taxa) showed that odontocete members of the traditional clade Cetacea are not related to mysticetes, which arise from a clade of mesonychids, hippos and desmostylians. Odontocetes arise from tenrecs.

A Jurassic squid choking hazard for Rhamphorhynchus

Hoffmann et al. 2020 reported in no uncertain terms,
“Pterosaurs ate soft-bodied cephalopods (Coleoidea).”

Immediately after, Hoffmann et al. dialed it back a bit,
when they wrote, “Here, we report the first evidence of a failed predation attempt
by a pterosaur on a soft-bodied coleoid cephalopod.”

Based on size alone,
the squid (PIMUZ 37358) was more than a mouthful according to this ‘to scale’ diagram (Fig. 1)…at least more than a stomachful.

Ask yourself:
could a Rhamphorhynchus of that size (none were larger) eat a squid of that size? Did the pterosaur fail at predation? Or did it change its mind after biting the squid out of curiosity or boredom and losing a tooth in the process?

Figure 1. Plesioteuthis squid in situ with tooth. Reconstructions of Plesioteuthis (above) and the n81 specimen attributed to the largest known Rhamphorhynhcus, which has a matching tooth. The question is: could that pterosaur eat that squid? Or did it change its mind after biting the squid?

Figure 1. Plesioteuthis squid in situ with tooth. Reconstructions of Plesioteuthis (above) and the n81 specimen attributed to the largest known Rhamphorhynhcus, which has a matching tooth. The question is: could that pterosaur eat that squid? Or did it change its mind after biting the squid? At the very top is the hard tissue gladius of the squid to scale. That’s a hard part that would have been especially hard to swallow.

You be the judge.
Hoffmann et al. 2020 have provided the pertinent information. Above are the predator and “prey” to scale. Other Rhamphorhynchus specimens are smaller, and the tooth could have fallen from a different alveolus (a larger tooth) on a smaller specimen. Lots of variables and unknowns here. Also consider the difficulty of swallowing that long gladius, a hard part homologous with the cuttle bone in a cuttlefish.

In any case,
watch what headline you put on your paper. Here the authors went for maximum impact. If, like these authors, you have to dial it back in the second sentence of your abstract,  maybe a more conservative headline should reflect that assessment. After all, a dietary mainstay is indeed different than a curious nibble… and relative size matters.

We looked at other pterosaur choking hazards
earlier here. Pterosaurs likely swallowed their prey whole. There is no indication that they tore squids apart, creating bite-sized pieces. Likewise there is no indication that pterosaurs were able to expand their stomach to accommodate oversize prey (Fig. 1).


References
Hoffman R, Bestwick J, Berndt G, Berndt R, Fuchs D and Klug C 2020. Pterosaurs ate soft-bodied cephalopods. http://www.nature.com/scientificreports (2020) 10:1230 | https://doi.org/10.1038/s41598-020-57731-2

The king mackerel is not a mackerel

Among commonly known near surface fish,
the king mackerel is more like a baraccuda or pike.

The king mackerel
(genus: Scomberomorus; Figs. 1, 2) enters the large reptile tree, LRT, 1643+ taxa) next to the deep sea scabbard fish (Aphanopus; Fig. 3), not the mackerel, Scomber, which entered the LRT a few days ago.

Figure 1. Scomberomorus cavalli is derived from barracuda and gives rise to seahorses and other taxa.

Figure 1. Scomberomorus cavalli is derived from barracuda and gives rise to seahorses and other taxa.

Scomberomorus cavalla (Cuvier 1829; 60cm) is the extant king mackeral or kingfish. King mackerals are derived from Sphyraena + Esox (barracuda and pike) in the LRT. Beside Aphanopus (Fig. 3), the king mackerel is basal to: flying fish + swordfish and  another branch: sticklebacks + sea horses.

Figure 2. The skull of the king mackerel, Scombermorus cavalla.

Figure 2. The skull of the king mackerel, Scombermorus cavalla.

The addition of this more plesiomorphic taxon
to the LRT makes the nesting of the more derived Aphanopus (Figs, 3, 4), a deep water taxon more understandable. Evidently, the LRT is still working, no matter what it has to work with, whether rare and autapomorphic deep sea taxa or common and plesiomorphic open ocean taxa.

Figure 3. Meter-long Aphanopus, the black scabbard fish, has a long, eel-like torso tipped with a tiny diphycercal tail.

Figure 3. Meter-long Aphanopus, the black scabbard fish, has a long, eel-like torso tipped with a tiny diphycercal tail.

Careful readers will note
the addition of several fish taxa (Fig. 4) shifted several traditional chondrichthyans to the lineage of bony fish, like Doliodus and Iniopteryx, helping to settle that long-standing issue of the genesis of bony fish.

Plus
the tripod fish (Bathypterois), the flying gurnard (Dactylopterus) and the sea robin (Prionotus) all moved closer to the frogfish (Antennarius), which also ‘stands’ on its pelvic fins. More insight into the sea robin and flying gurnard soon, as they forced a heretical interpretation to read the homologies on the ‘bony cheeks’ of these two scorpionfish clade taxa.

Figure 5. Subset of the LRT focusing on basal chordates, vertebrates and bony fish not related to tetrapods. Scomber and Istiophorus are new additions to the gold clade. Blue clade members ultimately lead to tetrapods after several dozen transitional taxa.

Figure 4. Subset of the LRT focusing on basal chordates, vertebrates and bony fish not related to tetrapods. Scomber and Istiophorus are new additions to the gold clade. Blue clade members ultimately lead to tetrapods after several dozen transitional taxa.

For returning readers, a reminder,
the fish skulls pictured here (e.g. Fig. 2) or in ReptileEvolution.com have been given tetrapod homology colors (pink for nasals, yellow for premaxillae, etc.), which enables the homologies discussed here. Years ago these colors were not standardized, but lately this practice has been maintained.


References
Cuvier GCLD 1829. Le Règne Animal distribué d’apres son organisation, pour servir de base a l’histoire naturelle des animaux et d’introduction a l’anatomie comparée. Avec figures dessinées d’après nature. Nouvelle édition, revue et augmentée. Tome V. Suite et fin des Insectes. Par M. Latreille. Déterville & Crochard, Paris, i-xxiv + 556pp.

wiki/Black_scabbardfish
wiki/King_mackerel
wiki/Scomber

Doliodus re-enters the LRT

Earlier I tried to understand
Doliodus latispinosus (Whiteaves, 1881; Maisey et al. 2018; originally Diplodus, problematicus (“problematic deceiver”) Woodward 1889; Fig. 1) and failed. Traditionally Doliodus has been considered part of the acanthodian-chondrichthyan (spiny shark to shark) transition, but the the large reptile tree (LRT 1643+ taxa) nests acanthodians far from chondrichthyans and Doliodus apart from both.

Figure 1. Doliodus skull and pectoral region with lateral reconstruction at right. Note the narrow pectoral region relative to the wide spread occiput. Apparently this fish had a narrower body than head.

Figure 1. Doliodus skull and pectoral region with lateral reconstruction at right. Note the narrow pectoral region relative to the wide spread occiput. Apparently this fish had a narrower body than head.

Maisey et al. 2018 reported,
“Based on these data, Doliodus and pucapampellids both fall outside the chondrichthyan crown, but their relative phylogenetic positions on the chondrichthyan stem are unclear.

The phylogenetic position of Doliodus seems less elusive; it possessed an ‘acanthodianlike’ complex of dermal spines, including pectoral fin spines, prepectoral, admedian, and prepelvic spines, and possibly dorsal and pelvic fin spines, in conjunction with numerous ‘chondrichthyan-like’ endoskeletal features and a heterodont ‘sharklike’ dentition. Doliodus can be viewed as a quintessential component of the evolutionary transition between ‘acanthodians’ and ‘conventionally defined chondrichthyans’, leaving little doubt that the chondrichthyan total group includes ‘acanthodians’ (now widely perceived to be a paraphyletic group, populating the basal part of the chondrichthyan stem).”

Figure 1. Skull of Iniopteryx in situ and reconstructed.

Figure 1. Skull of Iniopteryx in situ and reconstructed.

Doliodus re-enters the LRT with iniopterygids
(Fig. 2), a strange clade basal to chondrichtheys (ratfish) and elasmobranchs (sharks and kin). It is worthwhile to note that they, too, have a spine-stiffed pectoral fin, supporting an extended base of gracile rays…unlike spiny sharks. The eyes are enormous on a minimal snout. No squamosal is known.

This was probably a nocturnal bottom feeder
with a wide skull, wider than the narrow (as determined by the inter-fin distance) torso. Perhaps this flat taxon was transitional between low pectoral fins of most fish and the high-set pectoral fins that set iniopterygians apart.

Figure 2.I The Iniopterygidae include Iniopteryx, Promexyele, Iniopera and Sibyrhynchus. These reconstructions are from Zangerl and Case 1973 and the captions label them "tentative."

Figure 2. The Iniopterygidae include Iniopteryx, Promexyele, Iniopera and Sibyrhynchus. These reconstructions are from Zangerl and Case 1973 and the captions label them “tentative.”


Miller, Cloutier and Turner 2003 also reported on Doliodus.

They wrote, “This species has been truly problematic. Previously known only from isolated teeth, it has been identified as an acanthodian and a chondrichthyan [= sharks and rays]. This specimen is the oldest shark showing the tooth families in situ, and preserves one of the oldest chondrichthyan braincases. More notably, it shows the presence of paired pectoral fin-spines, previously unknown in cartilaginous fishes [= sharks and rays].” 

Check the cladogram (Fig. 3).
The LRT resolves this issue clearly. This is a novel hypothesis of interrelationships based on taxon inclusion. If anyone published the same interrelationships earlier, let me know so I can promote that citation.

Later, just Turner and Miller 2004 wrote,
“The most important feature of this fossil is its paired pectoral spines. These suggest that many isolated fossil spines might have belonged to sharks rather than acanthodians as previously believed. Features of the fossil blur the distinction between acanthodians and early chondrichthyans.”

“Textbooks still parrot the conventional thinking that no fossil sharks are found before the late Devonian, but this dogma ignores work from the last three decades. The oldest microfossils definitely attributable to sharks are scales in Silurian strata (440 mya) of Siberian and Arctic Russia. 

“Early Silurian deposits in the Tarim Basin of western China have also yielded fin spines associated with sharklike scales. Are these fossils true sharks? If so, the lineage was apparently toothless for millions of years. The first indisputable shark teeth do not turn up until about 50 million years after the appearance of these first putative shark scales in the late Ordovician.”

To answer that question: 
Yes. Some traditional sharks (Fig. 3, green clade) were toothless for millions of years before toothy sharks appeared.

The other answer to that question is:
check the cladogram (Fig. 3). Some traditional sharks (in the green clade) now appear outside the clade that includes ratfish and most sharks, rays and skates (pink clade) and some traditional sharks (peach clade) now appear basal to the basal dichotomy of bony fish (blue and gold clades).

Figure 4. Subset of the LRT focusing on basal vertebrates (fish). Esox and Ictalurus are highlighted. This cladogram reflects the latest results, which are still not completely resolving internal issues in the teleost clade. Tetrapods arise from the yellow clade at left.

Figure 4. Subset of the LRT focusing on basal vertebrates (fish). Esox and Ictalurus are highlighted. This cladogram reflects the latest results, which are still not completely resolving internal issues in the teleost clade. Tetrapods arise from the yellow clade at left.

In the LRT,
big-eyed, flat-skulled Doliodus (Fig. 4) nests with other big-eyed, spiny-finned iniopterygians in the clade that leads to bony fish, not sharks. Like the related Xenacanthus, Doliodus has double-tipped teeth.

Sharks are also known from a tooth battery,
a conveyer belt lineup of teeth waiting to rotate into place, as in Dolidus. The ‘millimeter-size teeth’ of Doliodus all point toward the tongue (Fig. 4), so the next teeth in the battery rotate to this position, rather than simply ascend or descend into position, as in tetrapods.


References
Maisey JG et al. (6 co-authors) 2018. Doliodus and Pucapampellids: Contrasting perspectives on stem chondrichthyan morphology. Chapter 5 in Evolution and Development of Fishes.
Miller RF, Cloutier R and Turner S 2003. The oldest articulated chondrichthyan from the Early Devonian period. Nature 435:501–504.
Turner S and Miller RF 2004. New ideas about old sharks. American Scientist 93:244–252.
Whiteaves JF. 1881. On some fossil fishes, Crustacea and Mollusca from the Devonian rocks at Campbellton, NB, with descriptions of five new species. Can Nat 10:93–101.
Woodward AS. 1889. Acanthodian fishes from the Devonian of Canada. Ann Mag Nat Hist 4:183–184.

 

The sailfish enters the LRT (and NOT with the swordfish)

Traditionally the sailfish
(Istiophorous) is considered a billfish, closely related to the marlin (Makaira), and then the swordfish (Xiphias).

By contrast, 
the large reptile tree (LRT, 1641 taxa; subset Fig. 5) nests the sailfish with the cobia (Rachycentron, Figs. 2,4), a Remora relative, rather than the swordfish, which the sailfish resembles by convergence, it turns out.

Figure 1. Istiophorus, the sailfish, nests with the cobria (Fig. 2) in the LRT, not with the swordfish.

Figure 1. Istiophorus, the sailfish, nests with the cobia (Fig. 2) in the LRT, not with the swordfish.

Istiophorus platypterus (Shaw 1792 in Shaw and Nodder 1792; 3m) is the extant sailfish and a relative of Rachycentron, the extant cobia (above). The rostrum is extended, convergent with another fast, open ocean predator, the swordfish, Xiphias. The anterior dorsal fin is larger than the lateral area of the fish itself. Teeth are absent. The pectoral fins are long and slender. The anal fin is divided in two. The vertebral column is composed of relatively few, but large vertebrae.

FIgure 1. The remora starts here: with the cobia (Rachycentron). Note the overall resemblance, lacking an adhesion disc. Instead six to nine tiny spine-hooks appear where an anterior dorsal fin appears on other fish.

Figure 2. The remora starts here: with the cobia (Rachycentron). Note the overall resemblance, lacking an adhesion disc. Instead six to nine tiny spine-hooks appear where an anterior dorsal fin appears on other fish.

Wikipedia reports,
“they [billfish] are also classified as being closely related to the mackerels and tuna within the suborder Scombroidei of the order Perciformes.”

By contrast,
mackerals and tuna are more primitive fish in the LRT. Swordfish are more derived, nesting with needlefish (Tylosaurus) and flying fish (Exocoetus), rather than sailfish. Marlins have not been tested yet because I can’t find a complete skull online.

Figure 3. Skull of Istiophorus, the sailfish with DGS colors applied.

Figure 3. Skull of Istiophorus, the sailfish with DGS colors applied. Compare to cobia skull in figure 4.

Rachycentron canadum (Kaup 1826; 2m) is the extant cobia. Like remora but without the adhesion disc, this fish also follows larger prey seeking the spoils and detritus. The first ‘dorsal fin’ has 6 to 9 short sharp spines. Females spawn 30 times a season, producing thousands of planktonic eggs 1.2mm in diameter.

Figure 4. Rachycentron, the cobia, skull with DGS colors applied. Compare to the sailfish in figure 3.

Figure 4. Rachycentron, the cobia, skull with DGS colors applied. Compare to the sailfish in figure 3.

BTW
The mackerel (genus: Scomber) also entered the LRT alongside Thunnus, the tuna, which it greatly resembles in every regard, other than size.

Figure 5. Subset of the LRT focusing on basal chordates, vertebrates and bony fish not related to tetrapods. Scomber and Istiophorus are new additions to the gold clade.

Figure 5. Subset of the LRT focusing on basal chordates, vertebrates and bony fish not related to tetrapods. Scomber and Istiophorus are new additions to the gold clade. 

Designed for reptiles,
the character list in the LRT is still working to separate fish as close in appearance as the swordfish and sailfish. So, please, don’t keep suggesting I expand the character list. It’s totally unnecessary.


References
Gregory WK and Conrad GM 1937. The comparative anatomy of the swordfish (Xiphias) and the sailfish (Istiophorus). The American Museum Novitates, 952:1-25.
Kaup JJ 1826.
Beiträge zu Amphibiologie und Ichthiyologie. Isis von Oken 19(1): 87-90.
Shaw G and Nodder FP 1792. Xiphias platypterus: The broadfinned swordfish. The naturalist’s miscellany, plate 88. 28 p. (Application to validate the nomen oblitum for the Indian Ocean sailfish (genus Istiophorus)

wiki/Istiophorus
wiki/Rachycentron

Kenomagnathus: what you can do with only 2 bones

Spindler 2020
reports on a new basal pelycosaur, Kenomagnathus scottae (ROM 43608; Upper Pennsylvanian, Late Carboniferous, Garnett, KS, USA; Figs 1-3) known from a single lacrimal and maxilla (with teeth) exposed in medial view (Fig. 1).

Figure 1. Kenomagnathus in situ from Spindler 2020.

Figure 1. Kenomagnathus in situ from Spindler 2020. The halo of organic matter is interesting.

From the abstract:
“This is the oldest known diastema in synapsid evolution, and the first reported from a faunivorous member that lacks a precanine step, aside from Tetraceratops. This unique precanine morphology occurred independently from similar structures in Sphenacodontoidea.” 

See Spindler’s freehand drawing
of the ‘true diastema’ (Fig. 2). 

Figure 2. Kenomagnathus maxilla and lacrimal with the rest of the skull restored in lateral view. Note the deep jugal, as in Ophiacodon (Figs. 3, 4). Spindler's freehand drawing indicates a deeper orbit, smaller jugal.

Figure 2. Kenomagnathus maxilla and lacrimal with the rest of the skull restored in lateral view. Note the deeper jugal (cyan), though not as deep as in Ophiacodon (Figs. 3, 4). For that reason the mandible of Ophiacodon was used in this restoration. Spindler’s freehand drawing indicates a deeper orbit, shallower jugal and smaller naris along with a larger mandible.

It is worth noting
that maxillary teeth shrink toward the naris in Ophiacodon (Fig. 3). A diastema may be present in Pantelosaurus (formerly Haptodus saxonicus, Fig.3). These pertinent taxa were not illustrated in Spindler 2020.

Figure 3. Pertinent synapsid skulls to scale. The origin of the Pelycosauria + Therapsida is marked by phylogenetic miniaturization, as in so many other clade origins. Note the depth of the jugal in basal taxa here.

Figure 3. Pertinent synapsid skulls to scale. The origin of the Pelycosauria + Therapsida is marked by phylogenetic miniaturization, as in so many other clade origins. Note the depth of the jugal in basal taxa here.

Spindler’s freehand restoration
increased the size of the orbit and decreased the depth of the restored jugal. So this is yet another cautionary tale highlighting the danger in using freehand drawings in scientific studies.

The shallow jugal depth in the Spindler freehand restoration
is a key oversight. When repaired (Fig. 2) the semi-deep jugal of Kenomagnathus transitionally links deeper jugal Ophiacodon (Fig. 3) to shallower jugal Pantelosaurus and Haptodus (Fig. 3) at the base of Pelycosauria + Therapsida in the large reptile tree (LRT, 1642+ taxa). While running the risk of ‘Pulling a Larry Martin’, there are so few traits to consider here (Fig. 1) and none contradict the present hypothesis of interrelationships. All that puts Kenomagnathus in the lineage of synapsids leading to therapsids, mammals, primates and humans.


References
Spindler F 2020. A faunivorous early sphenacodontian synapsid with a diastema. Palaeontologia Electronic 23(1):a01. doi: https://doi.org/10.26879/1023
https://palaeo-electronica.org/content/2020/2905-early-sphenacodontian-diastema