A paper model of the ‘Discodactylus’ skull

Earlier a flat, but layered Adobe Photoshop plan of the skull of Discodactylus’ was presented (Fig. 1) and nested with the very similar anurognathid pterosaur, Vesperopterylus.

Figure 3. The skull of NJU-57003 reconstructed in animated layers for clarity. This is something the print media just cannot do as well. All elements are similar to those found earlier in other anurognathids.

Figure 1. The skull of NJU-57003 reconstructed in animated layers for clarity. This is something the print media just cannot do as well. All elements are similar to those found earlier in other anurognathids.

Here
a paper, paste and tape model of this plan is presented (Figs. 2, 3), made from a print out of the elements in figure 1.

Figure 1. Paper reconstruction of the Discodactylus skull and mandibles.

Figure 2. Paper reconstruction of the Discodactylus skull and mandibles. Yes, the dentary teeth don’t make sense. They are scattered in situ and this is not corrected here.

The extremely fragile skull
held together from below by slender palatal bones (maxillary palatal rods and hyoids not shown) provides a solution for a flying animal with a wide, rattlesnake-like gape.

Figure 3. Another view of the paper reconstruction of the skull and mandibles of Discodactylus.

Figure 3. Another view of the paper reconstruction of the skull and mandibles of Discodactylus.

Discodactylus megasterna (Yang et al. 2018; Middle-Late Jurassic; NJU-57003) is a complete skeleton of a disc-skull anurognathid with soft tissue related to Vesperopterylus (below). The sternal complex is quite large to match the wider than tall torso. Distinct from other anurognathids, m4.1 does not reach the elbow when folded.

This specimen was featured in a report (Yang et al. 2018) on pterosaur filaments that incorrectly aligned pterosaurs with feathered dinosaurs, rather than their true ancestors, the filamentous fenestrasaurs, Sharovipteryx and Longisquama.

Figure 4. Vesperopterylus skull reconstructed from color data traced in figure 3.

Figure 4. Vesperopterylus skull reconstructed 

Figure 2. Vesperopterylus reconstructed using original drawings which were originally traced from the photo. Manual digit 4.4 is buried beneath other bones and reemerges to give its length. Pedal digit 1 turns laterally due to metacarpal arcing and taphonomic crushing. There is nothing reversed about it. 

Figure 5. Vesperopterylus reconstructed using original drawings which were originally traced from the photo. Manual digit 4.4 is buried beneath other bones and reemerges to give its length. Pedal digit 1 turns laterally due to metacarpal arcing and taphonomic crushing. There is nothing reversed about it.

References
Yang et al. (8 co-authors) 2018. Pterosaur integumentary structures with complex feather-like branching. Nature ecology & evolution.

 

 

Resurrecting extinct taxa: Pareiasauria, Compsognathidae and Ophiacodontidae

Earlier we looked at
four clades thought to be extinct, but are not extinct based on their nesting in the large reptile tree (LRT, 1366 taxa). Today, three more:

Figure 2. Another gap is filled by nesting E. wuyongae between Bunostegos and Elginia at the base of hard shell turtles in the LRT.

Figure 1. Another gap is filled by nesting E. wuyongae between Bunostegos and Elginia at the base of hard shell turtles in the LRT.

Pareiasauria
According to Wikipedia, “Pareiasaurs (meaning “cheek lizards”) are an extinct group of anapsid reptiles classified in the family Pareiasauridae. They were large herbivores that flourished during the Permian period.”

In the LRT two clades of turtles (Fig. 1) are derived in parallel from two small horned pareiasaurs.

Figure 1. Lately the two clades based on two specimens of Compsognathus (one much larger than the other) have merged recently.

Figure 2.  Lately the two clades based on two specimens of Compsognathus (one much larger than the other) have merged recently.

Compsognathidae
According to Holtz 2004, “The most inclusive clade containing Compsognathus longipes but not Passer domesticsus.” Traditionally Compsognathus nests outside the Tyrannoraptora, a clade that traditionally leads to birds.

In the LRT Compsognathus specimens nest at the base of several theropod clades (Fig. 2) including the tyrannosaurs and Mirischia, Ornitholestes and the feathered theropods leading to birds.

Figure 1. Varanosaurus, Ophiacodon, Cutleria and Ictidorhinus. These are taxa at the base of the Therapsida. Ophiacodon did not cross into the Therapsida, but developed a larger size with a primitive morphology. This new reconstruction of Ophiacodon is based on the Field Museum (Chicago) specimen. Click to enlarge.

Figure  3. Varanosaurus, Ophiacodon, Cutleria and Ictidorhinus. These are taxa at the base of the Therapsida. Ophiacodon did not cross into the Therapsida, but developed a larger size with a primitive morphology. This new reconstruction of Ophiacodon is based on the Field Museum (Chicago) specimen. Click to enlarge.

Ophiacodontidae
According to Wikipedia, “Ophiacodontidae is an extinct family of early eupelycosaurs from the Carboniferous and Permian. Ophiacodontids are among the most basal synapsids, an offshoot of the lineage which includes therapsids and their descendants, the mammals. The group became extinct by the Middle Permian.”

In the LRT Ophiacodon (Fig. 3) and Archaeothyris, neither members of the Pelycosauria, are more directly related to basal therapsids, including derived the therapsids: mammals.

References
Holtz TR 2004. Basal tetanurae. PP. 71–110 in The Dinosauria, U of California Press.

/wiki/Pareiasaur
wiki/Ophiacodontidae

 

Resurrecting extinct taxa: Creodonta, Mesonychidae, Desmostylia and Gephyrostegidae

Taxonomy
“the branch of science concerned with classification, especially of organisms; systematics.”  Taxon: a taxonomic group of any rank, such as a species, family, or class.

The large reptile tree
(LRT, 1366 taxa) has resurrected several taxa (in this case, clades) long thought to be extinct.

Figure 1. Adding Sinopa to the LRT nests it here, between the extant quoll (Dasyurus) and the extant Tasmanian devil (Sarcophilus).

Figure 1. Members of the traditionally extinct Creodonta include the extant quoll (Dasyurus) and the extant Tasmanian devil (Sarcophilus).

Creodonta
According to Wikipedia: “Creodonta” was coined by Edward Drinker Cope in 1875. Cope included the oxyaenids and the viverravid Didymictis but omitted the hyaenodontids. In 1880. he expanded the term to include MiacidaeArctocyonidaeLeptictidae (now Pseudorhyncocyonidae), OxyaenidaeAmbloctonidae and Mesonychidae. Cope originally placed creodonts within the Insectivora. In 1884, however, he regarded them as a basal group from which both carnivorans and insectivorans arose. Hyaenodontidae was not included among the creodonts until 1909. Over time, various groups were removed, and by 1969 it contained, as it does today, only the oxyaenids and the hyaenodontids.

In the LRT, Oxyaena and Hyaenodon are members of an extinct clade. However, Sinopa is considered a hyaenodontid, and it nests between the extant quoll (genus: Dasyurus) and the extant Tasmanian devil (genus: Sarcophilus). Sarkastodon is considered an oxyaenid and it nests as a sister to Sarcophilus. So… either the quoll and Tasmanian devil are living members of the Creodonta, or we’ll have to redefine the Creodonta.

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Figure 1. Rorqual evolution from desmostylians, Neoparadoxia, the RBCM specimen of Behemotops, Miocaperea, Eschrichtius and Cetotherium, not to scale.

Desmostylia
According to Wikipedia: “Desmostylians are the only known extinct order of marine mammals. The Desmostylia, together with Sirenia and Proboscidea (and possibly Embrithopoda), have traditionally been assigned to the afrotherian clade Tethytheria, a group named after the paleoocean Tethys around which they originally evolved. The assignment of Desmostylia to Afrotheria has always been problematic from a biogeographic standpoint, given that Africa was the locus of the early evolution of the Afrotheria while the Desmostylia have only been found along the Pacific Rim. That assignment has been seriously undermined by a 2014 cladistic analysis that places anthracobunids and desmostylians, two major groups of putative non-African afrotheres, close to each other within the laurasiatherian order Perissodactyla.”

In the LRT, desmostylians are indeed derived from anthracobunids, which, in turn, are derived from hippos and mesonychids. Mysticeti, the clade of baleen whales are derived from desmostylians. So… baleen whales are extant desmostylians.

Figure 3. Four mesonychids to scale. Here Mesonyx, Anthracobune, Paleoparadoxia and Hippopotamus are compared.

Figure 3. Four mesonychids to scale. Here Mesonyx, Anthracobune, Paleoparadoxia and Hippopotamus are compared.

Mesonychidae
According to Wikipedia, “Mesonychidae is an extinct family of small to large-sized omnivorouscarnivorous mammals closely related to cetartiodactyls (even-toed ungulates & cetaceans) which were endemic to North America and Eurasia during the Early Paleocene to the Early Oligocene. The mesonychids were an unusual group of condylarths with a specialized dentition featuring tri-cuspid upper molars and high-crowned lower molars with shearing surfaces. They were once viewed as primitive carnivores, like the Paleocene family Arctocyonidae, and their diet probably included meat and fish. In contrast to this other family of early mammals, the mesonychids had only four digits furnished with hooves supported by narrow fissured end phalanges.”

In the LRT, mesonychids include hippos and baleen whales. So, they are extant mesonychids. On the other hand, Arctocyonidae includes Arctocyon, which nests in the unrelated marsupial clade, Creodonta (see above). Certain other traditional mesonychids, like Sinonyx and Andrewsarchus, are not mesonyhids, but nest with the elephant shrew, Rhychocyon, close to tenrecs.

Figure 1. Silvanerpeton and Gephyrostegus to the same scale. Each of the two frames takes five seconds. Novel traits are listed. This transition occurred in the early Viséan, over 340 mya. Gephyrostgeus is more robust and athletic with a larger capacity to carry and lay eggs.

Figure 1. Silvanerpeton and Gephyrostegus to the same scale. Each of the two frames takes five seconds. Novel traits are listed. This transition occurred in the early Viséan, over 340 mya. Gephyrostgeus is more robust and athletic with a larger capacity to carry and lay eggs.

Gephyrostegidae
According to Wikipedia, “Gephyrostegidae is an extinct family of reptiliomorph tetrapods from the Late Carboniferous including the genera GephyrostegusBruktererpeton, and Eusauropleura.”

In the LRT, Gephyrostegus is the last common ancestor of the Amniota (= Reptilia). So… gephyrostegids include all living mammals, archosaurs (crocs + birds) and lepidosaurs.

References

wiki/Gephyrostegidae
wiki/Mesonychidae
wiki/Desmostylia

Basal placentals illustrated in phylogenetic order

Eutherian (= placental) mammals
are divided into clades like Primates, Ungulata, Carnivora, etc. Known basal taxa for each of these clades are related to one another in a ladder-like fashion, each one nesting at the base of a bushy clade in the large reptile tree (LRT, 1366 taxa).

Today,
an illustration of skeletons (Fig. 1) and skulls (Fig. 2) in phylogenetic order documents the minor changes (microevolution) between basal taxa that nest at the bases of several increasingly derived placental clades.

FIgure 1. Skeletons of taxa that nest at the bases of several major placental clades, divided between Cretaceous and Paleocene taxa.

FIgure 1. Skeletons of taxa that nest at the bases of several major placental clades, divided between Cretaceous and Paleocene taxa, divided by four different scales. Basal taxa are several degrees of magnitude smaller.

The following placental skulls are not to scale
yet continue to demonstrate the minor changes (microevolution) that occur at the bases of several major placental clades. For instance, Chriacus is basal to bats, while Maelestes is basal to odontocete whales. It is difficult, if not impossible, to determine such future developments in these basal taxa without the benefit of a wide gamut analysis, like the LRT.

Figure 2. A selection of placental skulls in phylogenetic order and divided into Cretaceous and Paleocene taxa.

Figure 2. A selection of placental skulls in phylogenetic order and divided into Cretaceous and Paleocene taxa.

The lesson for today:
Sometimes quantity, without firsthand observation, is needed to put together the ‘Big Picture’ before one is able to pick apart the details that each specific specimen reveals during firsthand study. Traditionally paleontologists have been putting the latter ahead of the former by (too often) excluding pertinent taxa revealed and documented by the more generalized and wide gamut phylogenetic analysis provided by the LRT. Like Yin and Yang, both must be considered. ‘Avoid taxon omission‘ is the single most important rule when constructing a cladogram of interrelationships.

References
See ReptileEvolution.com and links therein.

‘Taeniodonta’ is polyphyletic, part 4: Ectoganus, Stylinodon and Psittacotherium

These three bear-sized aquatic wolverines,
Ectoganus (Fig. 5), Stylinodon (Fig. 1) and Psittacotherium (Fig. 2), are traditional members of the invalidated polyphyletic (Fig. 3) clade ‘Taeniodonta’. We looked at other nestings for former taeniodonts earlier here, here and here. The large reptile tree (LRT, 1365 taxa) recently nested fanged Machaeroides basal to these taxa, rather than with its traditional marsupial sister, Oxyaena. Taxon exclusion kept the real sisters apart until now.

Figure 1. Stylinodon skull. Note the transverse premaxilla, a trait of the Carnivora.

Figure 1. Stylinodon skull. Note the transverse premaxilla, a trait of the Carnivora.

Stylinodon mirus (Marsh 1874; middle Eocene, 45 mya) was originally considered a taeniodont, perhaps derived from the basal phenacodont, Onychodectes. Here it nests within Carnivora in the clade of Mustela the living mink, Gulo the living wolverine and Ursus the living polar bear. The largest anterior teeth are canines. The peg-like molars also continued growing throughout life. There were twice as many molars (4), each with a single root, as in the two double rooted molars of the mink. The teeth continued growing throughout life, as in edentates like Glyptodon. Large claws indicate that digging remained part of its lifestyle.

Figure 7. Psittacotherium in various views.

Figure 7. Psittacotherium in various views.

Psittacotherium multifragum (Cope 1862; Paleocene, 60mya; 1.1m length) is a related taxon with canine teeth transformed into a parrot-like rostrum. Wortman 1896 considered it a type of ground sloth and a member of the Edentata (= Xenarthra).

Figure 3. Subset of the LRT labeling several traditional taeniodonts in red, indicating the traditional clade Taeniodonta is polyphyletic and should therefore be abandoned.

Figure 3. Subset of the LRT labeling several traditional taeniodonts in red, indicating the traditional clade Taeniodonta is polyphyletic and should therefore be abandoned.

Ectoganus copei (Schoch 1981; USNM 12714; early Eocene) is a sister to Stylinodon with a longer, lower skull, two upper incisors and a kinked maxilla.

Figure 5. Ectoganus nests with Stylinodon and Psittacotherium within the Carnivora, derived from Gulo, the wolverine.

Figure 5. Ectoganus nests with Stylinodon and Psittacotherium within the Carnivora, derived from Gulo, the wolverine.

Even as recently as 2013, Williamson and Brusatte
supported the traditional clade ‘Taeniodonta’, but only by the ‘authority’  of untested tradition (they employed the dataset and analysis of Rook and Hunter 2013).

Here we test from a wide gamut of taxa,
which minimizes the possibility of taxon exclusion. There’s no need to repeat a rumor, tradition or paradigm without a thorough testing in the LRT. The big picture is missing in traditional paleontology. That’s what the LRT is here for.

Again, this is low hanging fruit,
ignored by traditional paleontologists due to the easy sin of omission: taxon exclusion.

References
Cope ED 1882. A new genus of Tillodonta. The American Naturalist, 16: 156–157.
Rook DL and Hunter JP 2013. Rooting around the eutherian family tree: the origin and relations of the Taeniodonta. Journal of Mammal Evolution
DOI 10.1007/s10914-013-9230-9
Schoch RM 1983. Systematics, functional morphology and macroevolution of the extinct mammalian order Taeniodonta. Peabody Museum of Natural History Bulletin 42: 307pp. 60 figs. 65 pls.
Williamson TE and Brusatte SL 2013. New specimens of the rare Taeniodont Wortmania (Mammalia: Eutheria) from the San Juan Basin of New Mexico and Comments on the Phylogeny and Functional Morphology of “Archaic” Mammals. PLoS ONE 8(9): e75886. doi:10.1371/journal.pone.0075886
Wortman JL 1896. Psittacotherium, a member of a new and primitive suborder of the Edentata. Bulletin of the American Museum of Natural History 8(16):259–262.

wiki/Psittacotherium

 

 

A big sister for cat-like Oxyaena: Australohyaena

Figure 1. Australohyaena, a big sister to the cat-like marsupial, Oxyaena, in the LRT.

Figure 1. Australohyaena, a big sister to the cat-like marsupial, Oxyaena, in the LRT. That’s on oddly low jaw glenoid. Distinct from other marsupials, the jugal might NOT have extended to the jaw joint. Originally the frontals were considered nasals.

Australohyaena antiqua (Forasiepi et al. 2014; Late Oligocene; UNPSJB PV 113; Fig. 1) was originally nested with Borhyaena, but here nests with a previously untested taxon, Oxyaena (Fig. 1). Australohyaena is larger and more robust, but the orbit is no larger. The horizontal bar jaw joint makes the jaw a simple hinge with not transverse action possible. The jaw joint falls below the tooth row. The frontals were originally considered nasals.

If you think
marsupial Australohyaena looks like a placental lion (genus: Panthera leo), I agree with you (Fig. 2).

Figure 1. Panthera leo skull and skeleton. This taxon nests basal to hyenas + wolves.

Figure 2. Panthera leo skull and skeleton. This taxon nests basal to hyenas + wolves.

References
Forasiepi AM, Babot MJ and Zimicz N 2014. Australohyaena antiqua (Mammalia,
Metatheria, Sparassodonta), a large predator from the Late Oligocene of Patagonia, Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2014.926403

wiki/Australohyaena: no entry yet.

Looking for an outgroup to Multituberculata

As in the Pterosauria, the Chelonia, the Serpentes and the Archosauria,
traditional paleontologists have searched in vain for the closest known relatives of multituberculate mammals.

According to Kielan-Jaworowsak and Hurum 2001
(citations removed here:), “Finding an outgroup for the Multituberculata, is the first difficulty which one encounters in an attempt at phylogenetic analysis of this order. The problem is that the origins of the Multituberculata are obscure and in recent phylogenetic analyses of early mammals, multituberculate relationships have been a subject of vigorous controversy.”

“Traditionally palaeontologists believed that multituberculates might have originated from cynodonts independently from all other mammals, or diverged from other mammals at a very early stage of mammalian evolution. The multituberculate structure was so radically distinctive throughout their history that it seems hardly possible that they are related to other mammals except by a common origin at, or even before, the class as such.

More recently the idea that multituberculates might be a sister taxon of all other mammals has been supported. On the other hand, studies of the last two decades on the skull structure of multituberculates and other early mammals demonstrated the homogeneity of the internal structure of the skull and vascular system of all mammals, including multituberculates. The same concerns the discovery of multituberculate ear ossicles, which display the same pattern as those of all other mammals. The notion that multituberculates might form a sister taxon of all other mammals is related to the idea that they are close relatives to the Haramiyidae, a family represented until recently only by isolated teeth, with numerous cusps arranged in longitudinal rows, known from the Late Triassic and Early Jurassic mostly in Europe.”

Figure 1. Haramiyavia reconstructed and restored. Missing parts are ghosted. Three slightly different originals are used for the base here. The last appears to be the least manipulated and it appears to fit the premaxilla better.  The fourth maxillary tooth appears to be a small canine. The groove on the dorsal premaxillary appears to be for the nasal, not the septomaxilla. Parts are taken from both mandibles

Figure 1. Haramiyavia reconstructed and restored. Missing parts are ghosted. Three slightly different originals are used for the base here. The last appears to be the least manipulated and it appears to fit the premaxilla better.  The fourth maxillary tooth appears to be a small canine. The groove on the dorsal premaxillary appears to be for the nasal, not the septomaxilla. Parts are taken from both mandibles. Note the primitive ear bones, still acting as jaw bones. There is little to nothing here that links this genus to any multituberculate, which all have modern placental ear bones.

Continuing…
“Haramiyavia has been interpreted as having orthal jaw movement. On this basis Jenkins et al. excluded the Haramiyida from the Allotheria, which have propalinal (fore-and-aft) movement of the dentary and backward (palinal) power stroke. In turn Butler (2000) revised all known allotherians and argued that dental resemblance supports the hypothesis that the Multituberculata originated from the Haramiyida.”

“Finally, the most recent analyses of mammalian relationships, including analysis of the skeleton of a symmetrodont Zhangheotherium (Hu et al. 1997), and the skeleton of the eutriconodont Jeholodens (Ji et al. 1999), did not support multituberculate-therian sister-group relationship. In both of these papers the Multituberculata are placed between Monotremata (Ornithorhynchus) and Symmetrodonta (Zhangheotherium), being a sister taxon of all the Holotheria.”

“It should be pointed out that none of these analyses took into account the structure of the brain, which, as argued by Kielan-Jaworowska (1997), is one of several characters neglected in phylogenetic analyses of early mammals. The multituberculate brain, designated cryptomesencephalic (characterised by an expanded vermis, no cerebellar hemispheres, and lack of the dorsal midbrain exposure) is very different from that in Theria, which originally had eumesencephalic brains (characterised by a wide cerebellum with extensive cerebellar hemispheres and large dorsal midbrain exposure). The cryptomesencephalic brain characteristic of multituberculates otherwise occurs only in eutriconodonts.

Rugosodon eurasiaticus (Yuan et al. 2013, Late Jurassic, the size of a chimpmunk) is the oldest multituberculate and it is represented by a complete skeleton. Teeth and ankle evidence indicate it was an omnivore and arboreal.

Figure 2. Rugosodon eurasiaticus (Yuan et al. 2013, Late Jurassic, the size of a chimpmunk) is the oldest multituberculate and it is represented by a complete skeleton. Teeth and ankle evidence indicate it was an omnivore and arboreal.

The authors were not aware of most recent news on mammal brains.
Gilissen and Smith 2012 reported, “The terms cryptomesencephalic and eumesencephalic brains may have to be abandoned in light of a new interpretation of multituberculate and eutriconodontan endocasts. Our observations indicate that it is not the superior cistern but most probably the cerebellar vermis that makes a clearly visible impression on the posterior part of the endocranial casts of all extant and fossil mammals examined, including multituberculates and eutriconodonts.” 

 Kielan-Jaworowsak and Hurum 2001 continue:
“Another character neglected until recently in phylogenetic analyses of early mammals involves the foot structure. In the multituberculate foot the middle metatarsal is abducted from the longitudinal axis of the tuber calcanei, while the calcaneus contacts distally the 5fth metatarsal. This type of foot appeared at that time to be unique among mammals, but Ji et al. 1999 described a similar type of foot in the eutriconodont Jeholodens. It follows that there are two groups of characters related to brain and foot structure, which ally multituberculates with eutriconodonts.”

Re: the foot: 
It looks like Jeholodens has a basal tarsus because distal tarsal 4 is not wide enough to double as a distal tarsal 5, as it does in the marsupial, Didelphis. A quick peek at RattusVulpavus and Onychonycteris shows that these placental taxa likewise do not widen distal tarsal 4 to back up pedal digit 5. Comparable pedes among other tritylodontids are hard to find.

Dental traits can converge, just like any other traits.
(Remember ododontocetes have simple cones). Haramiyavia is tested along with 1360 other possible multituberculate sisters. In the large reptile tree Haramivavia nests basal to mammals apart from multituberculates. Multituberculates nest within Glires, closest to plesiadapids and rodents.

We looked at rodents
and multituberculates earlier here with lots of details (Fig. 3).

Figure 3. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT.

Figure 3. Comparing multituberculate origins: Cziki-Sava et al. vs. LRT.

In private correspondence with an early mammal expert,
I received the following reply based on evidence that multituberculates were related to rodents, rather than Haramiyida:  “Nice to hear from you. Honestly, this idea is so far out that I’m apoplectic. Yes, of course it’s worth reconsidering “conventional wisdom.” But the relationships of these groups within major clades are so well established that I see no point in considering the matter…beyond looking at relationships of plesiadapids within Eutheria. Anyway, good luck with your work!”

Sadly, this shows
some paleontologists are unwilling to test alternate hypotheses. Some would rather dismiss the obvious.

References
Kielan-Jaworowska Z and Hurum JH 2001. Phylogeny and Systematics of multituberculate mammals. Paleontology 44, 389–429.