SVP abstracts 2017: Eudibamus forelimb description

Sumida et al. 2017 bring us new information
on the pectoral region of Eudibamus, (Figs. 1,2) an early likely biped in the sprawling manner of the unrelated extant iguanian lizards, Chlamydosaurus and Basiliscus by convergence.

Unfortunately,
Sumida et al. continue to cling to the invalidated tradition that Eudibamus is a bolosaurid, largely based on convergent tooth shapes and taxon exclusion in their analyses.

Figure 1. Basal diasids and proto-diapsids. Largely ignored these putative synapsids actually split from other synapsids while retaining the temporal fenestra trait that serves as the basis for the addition of upper temporal fenestra in diapsids. Included here are Protorothyris, Archaeovenator, Mycterosaurus, Heleosaurus, Mesenosaurus, Broomia, Milleropsis, Eudibamus, Petrolacosaurus, Spinoaequalis, and Tangasaurus.

Figure 1. Basal diasids and proto-diapsids. Largely ignored these putative synapsids actually split from other synapsids while retaining the temporal fenestra trait that serves as the basis for the addition of upper temporal fenestra in diapsids. Included here are Protorothyris, Archaeovenator, Mycterosaurus, Heleosaurus, Mesenosaurus, Broomia, Milleropsis, Eudibamus, Petrolacosaurus, Spinoaequalis, and Tangasaurus.

From the Sumida et al. abstract
Eudibamus cursoris, a bolosaurid parareptile, from the Early Permian Tambach Formation (approximately 290 mybp), Thüringer Wald (Thuringian Forest), of central Germany, has been interpreted as the earliest known facultative biped. This was initially proposed based on the postcranial limb proportions in the type specimen (MNG [Museum der Natur, Gotha, Germany] 8852), but the forelimb itself has never been formally described. A nearly complete left, and partial right forelimb are preserved in the type specimen. The forelimb is less than 60% the length of the hindlimb. Only a thin, blade-like scapula is visible. Brachial, antebrachial, and manual elements are slender and elongate compared to those of other basal amniotes. The humerus has two well developed distal condyles with terminally facing articular facets. Delto-pectoral attachments were along a narrow ridge. The radius and ulna are nearly subequal in length. Conspicuously, the ulna lacks a well developed olecranon process. Carpals are proximodistally elongate compared to other basal amniotes. The intermedium and lateral centrale and the radiale and medial centrale articulate end-to-end, and their combined lengths equal that of the ulnare; the intermedium and radiale, and the medial and lateral centralia are equal in length. Four distal carpals are visible, it is unclear whether whether the fifth is truly absent or simply unossified. The distal carpal associated with digit two is reduced to a tiny pebble of bone, whereas that associated with digit four is largest and somewhat wedge shaped. Four metacarpals, likely equivalent to digits two-five, are present. The proximal portion of metacarpal two is present but length of the entire element cannot be determined. No elements of digit one can be seen, though its absence could be an artifact of preservation; however, the presence of only four distal carpals suggests Eudibamus may have had only four manual digits. Three phalanges are preserved in digits three and four. Both come to blunt tips and neither exhibits a significantly elongate penultimate element. The overall limb proportions seen in Eudibamus could suggest facultative bipedality or vertical clinging and leaping. However, vertical clingers and leapers normally have at least one is proportionately elongate manual digit and well-developed manual claws. Neither phalangeal proportions, nor the two well-developed terminal phalanges show such adaptations in Eudibamus and its interpretation as a facultative biped remains the most plausible interpretation of its postcranial anatomy.”

Figure 1. Click to enlarge. Eudibamus in situ (above), traced (middle) and reconstructed (below). The revised skull retains a large orbit and has a shorter rostrum.

Figure 1. Click to enlarge. Eudibamus in situ (above), traced (middle) and reconstructed (below). The revised skull retains a large orbit and has a shorter rostrum.

First of all,
Parareptilia has been invalidated as a monophyletic clade since 2012. 

Figure 2. Eudibamus skull revised here with new data compared to bolosaurids, on the left, and basal diapsids, on the right. Post crania for bolosaurids is very fragmentary. Bolosaurids are related to pareiasaurs and turtles, all derived from millerettids. Can you see why Eudibamus was confused with bolosaurids?

Figure 2. Eudibamus skull revised here with new data compared to bolosaurids, on the left, and basal diapsids, on the right. Post crania for bolosaurids is very fragmentary. Bolosaurids are related to pareiasaurs and turtles, all derived from millerettids. Can you see why Eudibamus was confused with bolosaurids?

Since 2011
Eudibamus has nested with other slender, speedy, basalmost archoauromorph diapsids (Araeoscelis, Petrolacosaurus and kin) (Fig. 1) in the large reptile tree, far from the squat, slow, bolosaurids, like Bolosaurus and Belebey that nest with diadectids and pareiasaurs.

Let’s look again
at the pectoral region and forelimb of Eudibamus as listed by Sumida et al. above. Note how many of these traits are also present in basal archosauromorph diapsid taxa and their outgroups shown in figure 1 above. Bolosaurids, by contrast, are known chiefly by skull material, so direct comparisons to forelimbs cannot be made.

Imagine the co-authors, grad students 
who disagree with Dr. Sumida on the phylogenetic position of Eudibamus, perhaps after testing a larger gamut of taxa or by reading this blog. All co-authors sign that they agree with what is in the abstract. This is how paleontology puts on blinders, clings to traditions and generally avoids rocking the hypotheses of senior professors.

Fortunately
non-academic renegades and independent researchers have no such restrictions, but are free to explore and experiment.

References
Sumida SS et al. 2017. Structure of the pectoral limb of the early Permian bolosaurid reptile Eudibamus cursors: further evidence supporting it as the earliest known facultative biped. SVP abstracts 2017.

Sumida 2009 Ted Talk video
What is Eudibamus?

Adding taxa to the Diadectes clade

Adding a few
and distinct Diadectes specimens (no two appear to be conspecific) opens the door to new insights into that corner of the cladogram. Some of the data are from 3D skull images with sutures delineated. Others are from firsthand observation. Some data are from drawings. Berman et al. 1992 made an interesting observation that prior authors illustrated the skull roof of Diadectes in a variety of ways (Fig. 1). The caption does not indicate that all were drawn from the same specimen. I suspect they were not.

Figure 1. How Berman et al. copied the illustrations of prior authors who each figured the skull roof of Diadectes. Perhaps these were several distinct specimens, not just one.

Figure 1. How Berman et al. copied the illustrations of prior authors who each figured the skull roof of Diadectes. Perhaps these were several distinct specimens, not just one. Not sure, at this point, which illustrations represent which specimens.

The Berman et al. phylogenetic analysis
included seven taxa, including two suprageneric taxa, Pelycosauria and Captorhinomorpha. They included only nine characters. The anamniote, Seymouria, was the outgroup. The first clade included Pelycosauria + (Limnoscelis +(Tseajaia and Diadectes). The second clade included Captorhinomorpha + Petrolacosaurus. The large reptile tree includes hundreds more taxa and characters. The pertinent subset is shown here (Fig. 2). It is also clear from the Berman et al. taxon set that they thought they were dealing with a small set of basal reptiles and pre-reptiles. In 2015 it is clear that they did not include the pertinent taxa they should have as some of these taxa are not related to any of the others except distantly.

Figure 2. How the large reptile tree lumps and splits the several Diadectes specimens now included here. Note that bolosaurids, including Phonodus, now nest within other Diadectes specimens.

Figure 2. How the large reptile tree lumps and splits the several Diadectes specimens now included here. Note that bolosaurids, including Phonodus, now nest within other Diadectes specimens.

Now, with current data
it is becoming increasingly clear that both bolosaurids and procolophonids nest within  a fully reptilian Diadectes clade. It is also clear that the genus Diadectes needs to be further split, as Kissel (2010) started to do by renaming Silvadectes and Oradectes from former Diadectes species.

Skeleton of Diadectes. Perhaps unnoticed are the broad dorsal ribs of this taxon, basal to Stephanospondylus, Procolophon and pareiasaurs.

Figure 3. Skeleton of Diadectes (UC 706, UC 1078). Perhaps unnoticed are the broad dorsal ribs of this taxon, basal to Stephanospondylus, Procolophon and pareiasaurs.

Also note
the placement of Stephanospondylus as a proximal sister taxon to the diadectids nesting at the base of the pareiasaurs (including turtles). Turtles are sisters to pareiasaurs and they ARE pareiasaurs because they are derived from pareiasaurs, just as birds are derived from theropod dinosaurs.

Figure 4. Click to enlarge. Stephanospondylus based on parts found in Stappenbeck 1905. Several elements are re-identified here. Note the large costal plates on the ribs, as in Odontochelys. The pubis apparently connected to a ventral plastron, not preserved. The interclavicle was likely incorporated into the plastron.

Figure 4. Click to enlarge. Stephanospondylus based on parts found in Stappenbeck 1905. Several elements are re-identified here. Note the large costal plates on the ribs, as in Odontochelys. The pubis apparently connected to a ventral plastron, not preserved. The interclavicle was likely incorporated into the plastron.

Like everyone who studies prehistoric reptiles
there is a day when you don’t know anything about a taxon and later there is a day when you are making contributions to Science. Those days keep on coming.

References
Berman DS, Sumida SS and Lombard E 1992. Reinterpretation of the Temporal and Occipital Regions in Diadectes and the Relationships of Diadectomorphs. Journal of Vertebrate Paleontology 66(3):481-499.
Kissel R 2010. Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha). Thesis (Graduate Department of Ecology & Evolutionary Biology University of Toronto).

SVP 15 – Erpetonyx. Still a milleropsid, not a bolosaurid

Modesto et al. 2015a
discuss Erpetonyx, which is still a sister to Milleropsis in the large reptile tree (not a bolosaur parareptile as originally described, Modesto et al. 2015b). And Milleropsis is not a millerosaur.

Note that Millerosauria is included as an ingroup taxon
Unfortunately Millerosaurus ornatus (Broom 1948, Watson 1957) Late Permian (Changhsingian, 30 cm est length) is based on a chimaera of over a dozen skeletons with many common elements distinct from one another. Millerosaurus has been removed from the large reptile tree. Milleropsis is a protodiapsid not related to Milleretta. Milleretta is likely the genera used for the original suprageneric taxon in the cladogram shown in Figure 1,

If this is too confusing, let me know and I’ll walk you through it.

This abstract
has already been published as a paper (Modesto et al. 2015b).

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

From the abstract
Erpetonyx arsenaultorum was recently erected for a single, nearly complete, and mostly articulated skeleton of a bolosaurian* parareptile** collected from the Gzhelian-age Egmont Bay Formation of Prince Edward Island. Erpetonyx arsenaultorum is autapomorphic in possessing 29 presacral vertebrae and a relatively small radiale, fifth distal carpal, and pisiform. The skull is characterized by the presence of plicidentine and by the absence of caniniform maxillary teeth. The neural arches closely resemble those of the Early Permian lanthanosuchian Delorhynchus cifelli in their broadly tongue-shaped zygapophyses, in which the lateral edges of the anterior zygapophyses pass posteriorly onto the lateral surface of the arch and form a conspicuous shelves, emphasized by an anteroventral pocket. The right carpus is well ossified. The preserved unguals are also well ossified, with a prominent flexor tubercle, a suboval proximal portion, and a stout, slightly ventrally curved tip. Together with the observation that the unguals are longer than their respective proximal phalanges, ungual morphology suggests adaptation to a fossorial or semi-fossorial lifestyle. Erpetonyx arsenaultorum is the oldest known amniote with digging adaptations, appearing ca. 3􀂱4 million years after the demise of th coal-swamp forests.

*Not a bolosaurian, but a milleropsid.
**Parareptile is an outmoded name based on traditional cladograms that have been falsified by the large reptile tree.

We looked at Erpetonyx earlier here in this blog.

References
Gow CE. 1972. The osteology and relationships of the Millerettidae (Reptilia: Cotylosauria). Journal of Zoology, London 167:219-264.
Modesto SP, Reisz RR, Macdougall MJ and Scott DM 2015a. Skeletal anatomy of the oldest known parareptile from the Upper Carboniferous of Priince Edward Island, Canada. Journal of Vertebrate Paleontology abstacts
Modesto SP, Scott DM, MacDougall MJ, Sues H-D, Evans DC, Reisz RR 2015b. The oldest parareptile and the early diversification of reptiles. Proceedings of the Royal Society B 282: 20141912. http://dx.doi.org/10.1098/rspb.2014.1912
Watson DMS 1957. On Millerosaurus and the Early History of the Sauropsida. Philosophical Transactions of the Royal Society of London Series B 240(673):325-400.

The Phonodus-Bolosaurus-Bashkyroleter connection

This post might be boring.
These are the unpopular, rarely studied plain-looking reptiles that ultimately gave rise to many of the most interesting clades.

Bolosaurids
are rarely studied, rarely included in phylogenetic analyses and little has been published on them. Bolosaurus and Belebey are the classic specimens. Long-legged Eudibamus has been added to this clade by traditional workers (Berman et al. 2000), but the large reptile tree nests it instead with basal diapsids, like long-legged Petrolacosaurus.

The busiest and most difficult corner
of the large reptile tree always seemed to be between Milleretta and Macroleter (Fig. 1).This subset of the tree also includes many previous enigmas here resolved, including  turtles.

Figure 1. A subset of the large reptile tree focusing on the taxa between Milleretta and Lepidosauriformes, perhaps the most difficult corner of the large reptile tree.

Figure 1. A subset of the large reptile tree focusing on the taxa between Milleretta and Lepidosauriformes, perhaps the most difficult corner of the large reptile tree.

Phonodus was originally considered a procolophonid.
(Modesto et al. 2010). Here (Fig. 2) Phonodus nests close to procolophonids, but closer to bolosaurids. As an Early Triassic taxon, Phonodus represents a late surviving member of a Late Pennsylvanian/Earliest Permian radiation that produced Early Permian diadectids and others. Based on its unusual teeth, Phonodus was highly derived.

Figure 1. Phonodus tracing. This turns out to be a basal bolosaurid.

Figure 2. Phonodus tracing. This turns out to be a basal bolosaurid, close to procolophonids. Note the deeply excavated squamosal. The naris was originally overlooked. 

A related taxon
Bashkyroleter (Fig. 3) was originally considered a nyctoleterid parareptile (not a valid clade). Here (Fig. 1) Bashkyroleter is basal to the bolosaur/diadectid/procolophon clade and pareiasaur/turtle clade AND the remainder of the lepidosauromorpha, including the lanthanosuchids proximally. So, it is a key taxon, largely overlooked except for one paper (Müller and Tsuji 2007) on reptile auditory capabilities.

Yes,
this solidification of the large reptile tree involved some topology changes. Science is self correcting. New data brings new insights. One of these new insights involved Bashykyroleter and a previously overlooked connection of the lateral to the naris. (Fig. 2).

Figure 2. Bashkyroleter appears to have a small naris/lacrimal connection.

Figure 3. Bashkyroleter appears to have a small naris/lacrimal connection as shown above. If anyone has a dorsal, occipital  or palatal view of this taxon, please send it along. Another deeply embayed squamosal. 

References
Berman, DS, Reisz RR, Scott D, Henrici AC, Sumida SS and Martens T 2000. Early Permian bipedal reptile. Science 290: 969-972.
Modesto SP, Scott DM, Botha-Brink J and Reisz RR 2010. A new and unusual procolophonid parareptile from the Lower Triassic Katberg Formation of South Africa. Journal of Vertebrate Paleontology 30 (3): 715–723. doi:10.1080/02724631003758003.
Müller J and Tsuji LA 2007. Impedance-Matching Hearing in Paleozoic Reptiles: Evidence of Advanced Sensory Perception at an Early Stage of Amniote Evolution. PLoS ONE 2 (9): e889. doi:10.1371/journal.pone.0000889. PMC 1964539. PMID 17849018

Erpetonyx, not a bolosaurid, but a milleropsid (protodiapsid)

Updated January 19, 2015 with new reconstruction and skull.

A new paper
by Modesto et al. (2014) describes a new Late Carboniferous reptile, Erpetonyx arsenaultorum (Fig. 1, ROM 55402, 303.7 to 298.9 Ma).

First in 20 years!
Erpetonyx arsenaultorum is the first Carboniferous reptile to be described in nearly two decades.

It made the news!
From the CBC website: “A fossil of a lizard-like creature found by a boy on a Prince Edward Island beach is a new species and the only reptile in the world ever found from its time, 300 million years ago, a new study shows.”

Complete but crushed,
with a disarticulated skull and extremities, this protodiapsid was considered a bolosaurid by Modesto et al, likely because it nests very close to Eudibamus, a basal diapsid they consider to be a bolosaurid. We looked at Eudibamus earlier here.

One mistake makes the next mistake easier to make.
Bolosaurids are turtle and pareiasaur sisters with crushing teeth. Note the long, narrow teeth of Erpetonyx (Fig. 1) more closely resemble those of Milleropsis (Fig. 2). This is an on-going issue.

Parareptile? 
Modesto et al. also support the paraphyletic clade Parareptilia and list Erpetonyx among them (Fig. 1). According to Modesto, et al., parareptilia (Fig. 1) is a clade nesting between Synapsida and Eureptilia (all the rest of the Amniota).

Unfortunately,
adding taxa, as in the large reptile tree, splits up most of the ‘parareptiles’. Mesosaurs nest with ichthyosaurs and thalattosaurs. The conventional millerosaurs, Milleroposis (Fig. 2) and Milleretta, are not related to each other. Procolophonids are derived from diadectids, not pareiasaurs. Australothyris is related to Milleretta and caseasaurs, not Lanthanosuchus. However, Lanthanosuchus, Microleter and Nyctiphruretus are related, not to far from bolosaurids, pareiasaurs and turtles.

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

The Late Carboniferous age
of Erpetonyx does precede that of its relatives, Broomia (Middle Permian) and Milleropsis (Early Permian), but a more derived taxon, Petrolacosaurus, is also Late Carboniferous in age.

Milleropsis, a largely forgotten taxon that displays possible bipedal traits at the base of the Diapsida.

Figure 1. Milleropsis, a largely forgotten taxon that displays possible bipedal traits at the base of the Diapsida. Note the long stiff tail without chevrons, as in Erpetonyx.

The carpus of Erpetonyx
is distinctive and quite similar to that of Broomia (Fig. 3). The original diagnosis of Erpetonyx makes note of the carpus. From the text: “A small, basal parareptile that possesses 29 pre sacral vertebrae (viz. five cervicals and 24 dorsals), relatively small carpal bones (the radiale and the pisiform are ca one-half the size of the ulnare and the fifth distal carpal, respectively), a femoral distal end with an epicondylar axis at 45º to the shaft, a fourth metatarsal with a relatively broad distal end, and well-developed unguals with prominent flexor tubercles.”

Figure 1. Broomia. A long-recognized sister to Milleropsis, an early possible biped. Check out those thighs!

Figure 3. Broomia. Another long-recognized sister to Milleropsis, an early possible biped close to Erpetonyx. Note the similarities in the carpus and tarsus.

Bolosauria
The authors resurrect the name Bolosauria, which was erected as an ordinal name by Kuhn to contain the family Bolosauridae Cope, 1878, and define it as a branch-based group: Bolosaurus striatus Cope, 1878 and all species related more closely to it than to Procolophon trigoniceps Owen, 1876. Unfortunately the last common ancestor of these two taxa in the large reptile tree is Saurorictus and Erpetonyx does not nest in this clade. The authors did not provide reconstructions.

Figure 6. Detail of skull tracings and reconstruction of Erpetonyx skull. The new data nests Erpetonyx closer to Milleropsis.

Figure 6. Detail of skull tracings and reconstruction of Erpetonyx skull. The new data nests Erpetonyx closer to Milleropsis. The prefrontal is broken up. The original frontal is now a lacrimal. 

References
Modesto SP, Scott DM, MacDougall MJ, Sues H-D, Evans DC and Reisz RR 2014. The oldest parareptile and the early diversification of reptiles. Proc. R. Soc. B 282:
20141912. http://dx.doi.org/10.1098/rspb.2014.1912