Danjiangia: not a chalicothere, not a brontothere…

It’s an early Eocene pig
according to the large reptile tree (LRT, 1003 taxa). A large gamut minimizes inclusion set bias and gains greater authority with every added taxon. It also reduces the average phylogenetic distance between taxa, all of which are species and individuals, not suprageneric taxa.

Figure 1. Danjiangia nests with the extant pig, Sus, in the LRT.

Figure 1. Danjiangia nests with the extant pig, Sus, in the LRT. Note the very low naris and nasal. The lost skull could have been elevated, as imagined here after phylogenetic analysis.

Danjiangia pingi (Wang 1995; early Eocene) was originally described as a basal chalicothere with brontothere traits. Then Hooker and Dashzeveg (2003) nested it as a basal brontothere (without including any other brontotheres). Mihlbacher 2008 and others used it as an outgroup to the brontotheres. The posterior skull is not known, but note the rise over the orbits suggesting a tall cranium, as in Sus (Fig. 2). Also note the very low naris below the low nasals. Usually you don’t see nasals so low, and perhaps that is due to taphonomic shifting.

Figure 2. Skull of the extant pig, Sus in several views.

Figure 2. Skull of the extant pig, Sus in several views. Note the elevated cranium and squamosal.

The long fused dentary 
of Danjiangia is a trait also shared with pigs and other taxa, like chalicotheres, by convergence.

Figure 1. Skeleton of Sus, the pig, a taxon commonly used as an outgroup for whales. In the LRT it is a sister to other even-toed ungulates, like Giraffa, not Odontoceti nor Mysticeti.

Figure 3. Skeleton of Sus, the pig. It provides good clues as to the missing postcranial skeleton of Danjiangia.

Sus the pig
(Fig. 3) provides good clues as to the missing postcranial skeleton of its sister taxon, Danjiangia. The other model for post-cranial details is the basal artiodactyl, Cainotherium (Fig. 4).

Fig. 1. Cainotherium nests at the base of the Artiodactyla or even-toed ungulates. I wonder if it had five fingers, even if vestiges, given that Ancodus, a derived artiodactyl, retains five fingers.

Fig. 4. Cainotherium nests at the base of the Artiodactyla or even-toed ungulates. I wonder if it had five fingers, even if vestiges, given that Ancodus, a derived artiodactyl, retains five fingers.

Why was the pig connection missed by others?
For the same reason that modern workers continue to include pterosaurs with archosaurs. It’s a tradition. Nobody wants to do the extra work of testing other candidate taxa. Nobody wants to acknowledge contrarian studies. Paleontology tends to run very slowly as we learned earlier here. Hail, hail the status quo!

Figure 1. Subset of the LRT focusing on ungulates, which split into three clades here.

Figure 5. Subset of the LRT focusing on ungulates, which split into three clades here. Note the nesting of Sus together with Danjiangia.

References
Beard KC 1998. East of Eden: Asia as an important center of taxonomic origination in mammalian evolution; pp. 5–39 in Beard and Dawson (eds.), Dawn of the Age of Mammals in Asia. Bulletin of Carnegie Museum of Natural History 34.
Mihlbachler MC 2004. Phylogenetic systematics of the Brontotheriidae (Mammalia, Perissodactyla). PhD dissertation. Columbia University. p. 757.
Mihlbachler MC 2008. Species taxonomy, phylogeny and biogeography of teh Brontotheriidae (Mammalia: Perissodactyla). Bulletin of the American Museum of Natural History 311:475pp.
Wang Y 1995. A new primitive chalicothere (Perissodactyla, Mammalia) from the early Eocene of Hubei, China. Vertebrata Palasiatica 33: 138–159.

Splitting up the Ungulates

Get ready for a good dose of heresy
brought to you by the large reptile tree (LRT 1003 taxa) a fully resolved online morphological study.

A little backstory
According to Wikipedia: Ungulates are any members of a diverse group of primarily large mammals that includes odd-toed ungulates such as horses and rhinoceroses, and even-toed ungulates such as cattlepigsgiraffescamelsdeer, and hippopotami.”

“However, in 2009 morphological and molecular[ work has found that aardvarks, hyraxes, sea cows, and elephants are more closely related to sengistenrecs, and golden moles than to the perissodactyls and artiodactyls, and form Afrotheria. Elephants, sea cows, and hyraxes are grouped together in the clade Paenungulata, while the aardvark has been considered as either a close relative to them or a close relative to sengis in the clade Afroinsectiphilia. This is a striking example of convergent evolution.

“There is now some dispute as to whether this smaller Ungulata is a cladistic (evolution-based) group, or merely a pheneticgroup (form taxon) or folk taxon (similar, but not necessarily related). Some studies have indeed found the mesaxonianungulates and paraxonian ungulates to form a monophyletic lineage, closely related to either the Ferae (the carnivorans and the pangolins) in the clade Fereuungulata or to the bats. Other studies found the two orders not that closely related, as some place the perissodactyls as close relatives to bats and Ferae in Pegasoferae and others place the artiodactyls as close relatives to bats.” 

About that last hypothesis ~
If I had recovered that relationship I would expect pitchforks and torches.

Today
the LRT presents a hypothesis of mammal relationships in which hippos nest apart from other artiodactyls and perissodactyls nest apart from those two, separated by the elephant/hyrax/manatee clade with the hyrax-like Ectocion at it base (Fig. 1).

Figure 1. Subset of the LRT focusing on ungulates, which split into three clades here.

Figure 1. Subset of the LRT focusing on ungulates, which split into three clades here.

Note:
Hippos do indeed nest with whales, but only the mysticete whales. And desmostylians separate hippos from mysticetes. Odontocetes, like Orcinus, had a separate ancestry as we learned earlier here. The even-toed artiodactyls nest together with pig-types toward the base and deer-types a little later. The odd-toed perissodactyls nest together.

There are no
tenrecs, aardvarks or golden moles in this sector of the LRT.

Ungulata is not a monophyletic cladistic group,
unless it also includes the elephants and whales with Mesonyx as a basal member, (a taxon close to the last common ancestor). I’m not the first one to come to this conclusion. Probably best just to drop this name from usage and realize that hooves appeared several times in mammal evolution.

A little extra study
cleared up the earlier Pappaceras issue. Now the nesting is more in accord with consensus with regard to the indricotheres, but they’re still closer to 3-toed horses than to 3-toed rhinos.

Also note:
the <50 Bootstrap scores surrounding Hyracotherum, a basal horse/rhino. I could only separate sister taxa by 2 steps. It takes at least 3 steps to bounce the Boostrap score over 50. Small steps. Small steps.

 

Chalicothere skulls to scale

Figure 1. Moropus elatus is a horse-sized chalicothere from the Miocene.

Figure 1. Moropus elatus is a horse-sized chalicothere from the Miocene. Note the large claws on the manus and smaller ones on the pes.

As we’ve seen before
there are several horse-like taxa in the mammal family tree. Known for over 150 years and worldwide in dispersal, the chalicotheres (Figs. 1-3) had claw-like hooves on an otherwise horse-like body and skull.

Figure. 2. Chalicothere skulls to scale. Lophiodon is an outgroup closer to tapirs.

Figure. 2. Chalicothere skulls to scale. Lophiodon is an outgroup closer to tapirs.

Because several taxa
in the large reptile tree have horse-like traits, the ability to split and lump these taxa is being taxed. Moreover, the outgroup for the chalicotheres has shifted with the addition of more closely related taxa.

Lophiodon
nests close to the base of the chalicotheres, close to tapirs and other extinct South American mammals.

Litolophus
(Fig. 2) is a basal chalicothere with round, hoof-like hooves. Basal taxa have four metacarpals. The fourth one is reduced on later taxa. What looks like a Pteranodon-like crest would have been layered with strong jaw muscles.

Tylocephalonyx
(Fig. 2) had a domed cranium, distinct from other chalicotheres.

Anisodon macedonicus 
(Fig. 2) had a short, primate-like face, distinct from other chalicotheres.

Anisodon grande
(Fig. 3) is another derived chalicothere with longer forelimbs, no tail and probably sat on its large buttocks while feeding.

Figure 3 Anisodon grande had longer forelimbs than hind limbs.

Figure 3 Anisodon grande had longer forelimbs than hind limbs.

More later
as the study proceeds…

References
Bai B, Wang Y-Q and Meng J 2010. New craniodental materials of Litolophus gobiensis (Perissodactyla, “Eomoropidae”) from Inner Mongolia, China, and phylogenetic analyses of Eocene chalicotheres. American Museum Novitates 3688: 27pp.
Colbert EH 1934. Chalicotheres from Mongolia and China in the American Museum. Bulletin of the American Museum of Natural History 67: 353–387.
de Blainville HMD 1849. Ostéographie ou description iconographique comparée du squelette et du système dentaire des Mammifères récents et fossiles – Genus Anoplotherium. 4 BB, Paris: J.B. Baillère, 66–70.
Kaup CC 1833. Description d’ossements fossiles de mammifère’s inconnus jusqu’ à-présent, qui se trouvent au Muséum grand-ducal de Darmstadt. Second cahier. – 1 – 31.Darmstadt (J.G.Heyer).
Lartet É 1851. Notice sur la colline de Sansan. Extrait de l’Annuaire du Département du Gers, année 1851. Auch: J.-A. Portes.
Marsh OC 1877. Notice of some new vertebrate fossils. American Journal of Arts and Sciences 14:249-256.

wiki/Chalicotherium
wiki/Litolophus
wiki /Moropus
wik/ Anisodon

Chongmingia: no longer an enigma bird

Revised November 1, 2020
with a reconstruction of Chongmingia (Fig. 1) with new insights into to pectoral girdle and manus along with a new nesting near the base of the scansoriopterygidae in the LRT (subset Fig. 2) close to Mei and Yi (Fig. 3).

Figure 1. Chongmingia tracing from Wang et al. alongside a reconstruction of the elements.

Figure 1. Chongmingia tracing from Wang et al. alongside a reconstruction of the elements.

Wang et al. 2016
reported on a head-less, ‘tail-less’ basal bird fossil, which they named Chongmingia (Fig. 1).

Unfortunately the team had some difficulty nesting Chongmingia.
They reported: “For the first analysis using the coelurosaurian matrix, the analysis produced 630 most parsimonious trees of 4523 steps (Consistency index = 0.266, Retention index = 0.578). The strict consensus tree placed Chongmingia within basal Avialae, and Chongmingia is the sister taxon of Ornithothoraces. For the second analysis focusing on phylogeny of Mesozoic birds, the analysis produced four most parsimonious trees of 1009 steps. The strict consensus tree places Chongmingia as the sister to all avialans except for Archaeopteryx, and thus Chongmingia represents the most primitive bird from the Jehol Biota uncovered to date and one of the most primitive Cretaceous birds known. However, this phylogenetic hypothesis was weakly supported by both Bremer and Bootstrap values.”

Unfortunately the team did not use several Solnhofen birds 
in their phylogenetic analysis. Perhaps if they did so, like the large reptile tree (LRT, 998 [now 1752] taxa) does, then they might have recovered a single tree in which Chongmingia nests within basal Scansoriopterygidae in the LRT (Fig. 2).

Figure 4. Subset of the LRT focusing on birds. Chongmingia is highlighted in yellow in the Scansoriopterygidae.

Figure 4. Subset of the LRT focusing on birds. Chongmingia is highlighted in yellow in the Scansoriopterygidae.

I was able to see in the published photo of Chongmingia

  1. a small string of diminishing caudal vertebrae
  2. the scapula and coracoid intertwined
  3. reidentified some disarticulated phalanges

Figure 3. Ambopteryx nests midway and is phylogenetically midway between the larger Yi and the smaller Scansoriopteryx. None of these taxa have an extra long bone in the arm.

Figure 3. Ambopteryx nests midway and is phylogenetically midway between the larger Yi and the smaller Scansoriopteryx. None of these taxa have an extra long bone in the arm.

Nesting at the base of the derived taxa,
Mei, Yi, and the several other scansoropterygids with a longer manual 3 than 2, Chongmingia (Fig. 1) is the first step toward that morphology. AND… there is no hint of a new, elongate carpal bone. That mistake remains a myth.

Such a small tail
like the similarly short-changed Yi, would not have accommodated many rectrices (tail feathers). There is no evidence of a pygostyle. Relatives don’t have a pygostyle.


References
Wang M, Wang X, Wang Y and  Zhou Z 2016. A new basal bird from China with implications for morphological diversity in early birds. Nature Scientific Reports 6, art. 19700, 2016.

wiki/Chongmingia

Cainotherium: a basal artiodactyl

This one everyone agrees on.
Cainotherium nests at the base of included artiodactyls in the large reptile tree (LRT).

Fig. 1. Cainotherium nests at the base of the Artiodactyla or even-toed ungulates. I wonder if it had five fingers, even if vestiges, given that Ancodus, a derived artiodactyl, retains five fingers.

Fig. 1. Cainotherium nests at the base of the Artiodactyla or even-toed ungulates. I wonder if it had five fingers, even if vestiges, given that Ancodus, a derived artiodactyl, retains five fingers.

Cainotherium renggeri (Bravard 1828, 1835; 30cm in length; Eocene to Early Miocene) was and is considered a rabbit-sized artiodactyl not far from the odd-toed ungulates, like the similarly-sharp-clawed Chalicotherium.

Note that a derived artiodactyl, Ancodus (Fig. 2) had five fingers, so one wonders if Cainotherium likewise had five.

Figure 1. Ancodus nests as a more derived sister to Sus and it retains digit 1 on the manus and pes.

Figure 1. Ancodus nests as a more derived sister to Sus and it retains digit 1 on the manus and pes.

References
Bravard A 1835. Monographie du Cainotherium, Levrault, Paris, 1835.
Heizmann EPJ 1999. Family Cainotheriidae, in : Rössner G.E., Heis- sig K. (éds), The Miocene Land Mammals of Europe, Pfeil, 1999, pp. 217–220.

wiki/Cainotherium

Pectodens: basal to tanystropheids and pterosaurs

It’s always good
to see another tritosaur. That’s the lineage that gave rise to a menagerie of taxa, including pterosaurs. That’s a heretical hypothesis of relationships recovered by the large reptile tree (LRT, 997 taxa).

Figure 1. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Figure 1. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Li et al. 2017 conclude:
“A new, small terrestrial tetrapod is described from the Middle Triassic of Yunnan, China. Pectodens zhenyuensis n. gen. n. sp. bears very characteristic elongate teeth forming a comb-like marginal dentition. The elongate cervicals of Pectodens zhenyuensis n. gen. n. sp. with low neural spines together with the morphology of the cervical ribs are features consistent with protorosaurs, such as Macrocnemus. However, the imperforate puboischiadic plate, simple rounded proximal tarsals, and a straight 5th metatarsal are primitive characteristics. Unlike tanystropheids, but in common with Protorosaurus (personal observation, N.C. Fraser, 2013), both lack a thyroid fenestra in the pelvis.”

Figure 2. Pectodens skull traced using DGS techniques and reassembled below.

Figure 2. Pectodens skull traced using DGS techniques and reassembled below. Here a quadratojugal process of the jugal is identified and other parts are assembled with greater accuracy than a freehand sketch (Fig. 1).

Pectodens zhenyuensis (Li et al. 2017; IVPP V18578; Anisian, Middle Triassic; 38cm in length) was originally considered a diapsid and a possible protorosaur. Here Pectodens nests between Macrocnemus and Langobardisaurus (Fig. 3). Originally the interclavicle, sternum and quadratojugal were overlooked.

Note the large orbit, the long metarsal 5 and the perforated pubis. The elongate caudal transverse processes anchor powerful leg muscles.

Occasionally within the Tritosauria
metatarsal 5 is not short, but elongate. It is always axially twisted. The pubis and ischium typically angle away from one another, but sometimes produce a thyroid fenestra. Tritosaurs have a sternum, like many other lepidosaurs do. Protorosaurs do not have a sternum.

Li et al. did not attempt a phylogenetic analysis.
Instead they made educated guesses as to the affinities of Pectodens, overlooking the variation present in related taxa revealed in a cladogram. Pulling a Larry Martin (highlighting or letting yourself get confused by one or two traits) is never a good idea. Better to let hundreds of traits determine the exact nesting of a taxon without bias. Let the taxa nest themselves. Let the convergent traits simply be convergent traits.

Earlier we looked at the pectoral girdle and sternum of Langobardisaurus, Huehuecuetzpalli and other tritosaurs. Pectodens fits right in.

The posterior maxillary teeth in Pectodens
are wider at their base presaging the grinding teeth found in Cosesaurus, basal pterosaurs and Langobardisaurus.

Note the way the fingers and toes
bend anteriorly during use. That’s a lepidosaur trait. Pectodens would have had sprawingling hind limbs given its simple femoral head. Tracks matching such curved toes are known from the Middle Triassic.

Li et al. considered Pectodens to be the first terrestrial taxon
from the its locality. And that’s definitely a probability. However, given that Tanystropheus and others may have been underwater bipedal predators (squid parts were found in their torso), let’s leave open the possibility that Pectodens was maybe dipping its toe in the water.

Figure 1. Subset of the LRT focusing on Tritosauria. Pectodens nests here basal to the Characiopoda (Tanystropheids + Fenestrasauria including pterosaurs).

Figure 1. Subset of the LRT focusing on Tritosauria. Pectodens nests here basal to the Characiopoda (Tanystropheids + Fenestrasauria including pterosaurs).

Let’s not continue to nest tanystropheids
with protorosaurs. Sure they share several traits by convergence, but they are not related to one another as determined by a large gamut analysis, the LRT.

References
Li C, Fraser NC, Rieppel O, Zhao L-J and Wang L-T 2017. A new diapsid from the Middle Triassic of southern China. Journal of Paleontology.7 pp. doi: 10.1017/jpa.2017.12