Mupashi migrator: a new Karenitid Therocephalian From Upper Permian Zambia

The first karenitid (Therapsida, Therocephalia) from the upper Permian of Gondwana and the biogeography of Permo-Triassic therocephalians

Authors:

Huttenlocker et al

Abstract:

Therocephalians were an ecologically diverse group of therapsids whose long stratigraphic record and widespread distribution during Permian and Triassic times make them important for understanding biogeographic patterns during a major faunal transition. Here, we describe a new therocephalian, Mupashi migrator gen. et sp. nov., from the upper Madumabisa Mudstone Formation (upper Permian) of Zambia's Luangwa Basin. The specimen has a long snout with a maxilla–vomerine contact on the hard palate, a high antecanine tooth count and numerous postcanines, and a conspicuous boss on the dentary angle whose structure is identical to that of the Russian baurioid Karenites. Additional endocranial anatomy, including palatal and braincase features, are revealed by high-resolution X-ray computed tomography and described in detail in light of the growing availability of tomographic data for therapsids. A phylogenetic analysis of 56 therapsid taxa and 136 cranial and postcranial characters recovers Mupashi as the sister taxon to Karenites, placing the pair between basal ictidosuchid-grade baurioids and the later Triassic bauriamorphs. Parsimony optimizations of geographic occurrences are ambiguous regarding the origination centers of therocephalian subclades. However, the patterns are suggestive of either (1) rapid, early dispersal events of Eutherocephalia and its major subgroups from a Laurasian center during the early–late Permian or, more likely, (2) within-province diversifications with occasional dispersal events occurring between provinces. Regardless, these associations strengthen the hypothesis that unknown but effective dispersal routes to high latitudes were available to therapsids and other tetrapods at least until early–late Permian times.

A Revision of Whaitsiid Therocephalian Theriognathus From Late Permian South Africa

Revision of the first therocephalian, Theriognathus Owen (Therapsida: Whaitsiidae), and implications for cranial ontogeny and allometry in nonmammaliaform eutheriodonts

Authors:

Huttenlocker et al

Abstract:

Historically, the whaitsiid therocephalian Theriognathus Owen was one of the earliest described nonmammalian therapsids, its morphology helping to link phylogenetically the Paleozoic synapsids of North America and southern Africa to their mammalian successors. However, decades of taxonomic over-splitting and superficial descriptions obscured the morphologic diversity of the genus, hindering its utility as a study system for the evolution of synapsid cranial function as well as its biostratigraphic significance in the Late Permian of southern Africa. Here, we revise the status and provenance of all the known specimens of Theriognathus from South Africa, Tanzania, and Zambia. We present both qualitative and quantitative support for the presence of a single morphospecies as proposed by some authors. Proportional differences in skulls that were previously ascribed to different morphotypes (‘Aneugomphius,’ ‘Notosollasia,’ ‘Moschorhynchus,’ and ‘Whaitsia’) are largely size-related and allometric trends are considered here in the context of jaw function and prey prehension. Our results suggest that the single species, Theriognathus microps, represented one of the most abundant Late Permian therocephalians in southern Africa and is consequently a potentially useful biostratigraphic marker for the upper Cistecephalus-lower Dicynodon Assemblage Zone transition (i.e., late Wuchiapingian). The wide range of preserved sizes in conjunction with recent paleohistological evidence supports that individuals spent much of their lives in an actively-growing, subadult phase. Later Dicynodon Assemblage Zone records (e.g., upper Balfour Formation) are unconfirmed as the genus was likely replaced by other theriodont predators (e.g., Moschorhinus) leading up to the Permo-Triassic boundary in the Karoo Basin of South Africa.

Once Upon the Permian: Therocephalians, the Near Mammals Before Mammals

Euchambersia, a potentially venomous akidnognathid eutherocephalian

Introducing the Therocephalians

It has been a long time since I wrote a therapsid post.  Part of the problem is there are two groups I find the most fascinating and want to write about.  However, they are incredibly diverse.  Far, far more so than either the dicynodonts or the gorgonopsids.  While the former filled niches of herbivores from those like gophers to giant cattle or rhinos and the latter were carnivores filling top or middle predator niches, the others fill virtually everything.    Herbivore, carnivore, omnivore, aquatic, arboreal, flying and more.  So, it's really hard to do a single post for them.  Those groups are the therocephalians and the cynodonts.  The latter encompass our modern mammals.  Some day, I'll get the cynodonts, but not today.  Today, I'll be covering the therocephalians.

Annatherapsis, an otter-like akidnognathid eutherocephalian

While the therocephalians are somewhat known from a couple of appearances in the popular media, in Primeval and Walking With Monsters, they are largely unknown in truth.  They were large and small.  Sabre toothed top predators and rodent-like herbivores.  They had a far greater range of bauplans than did either of the other two groups I have written about.  

Therocephalians ("beast heads") were the sister clade to cynodonts ("dog teeth"): meaning they are very closely related.  Cynodonts were the lineage that gave rise to and encompasses mammals.  Early on they were almost exclusively carnivorous, but after the Permian Mass Extinction they would go on to fill even more roles.  They would develop a number of traits in parallel to the cynodonts.  So much so, that it was long thought they were the ancestors of mammals through the Bauroids rather than cynodonts. Some of those features were the secondary palate, phalanges like those of mammals, evidence of warm bloodedness and even whiskers.

The therocephalians existed from the Middle Permian (Capitanian) through the early Middle (Anisian) Triassic.  They diversified after the Guadalupian Mass Extinction, along with many other advanced therapsid forms, survived the Permian Extinction and then made it into the early Middle Triassic.  They seem to have been victims of whatever changed over the ecology from being a mix of therapsids and archosaurs in the megafauna to an archosaur dominated megafauna in the Late Triassic.  Some have speculated they were merely outcompeted by cynodonts and the rising archosauriformes.  They are last recorded in Namibia during the Anisian Triassic with Microgomphodon.

Therocephalians were fairly common.  They seem to have been discovered on all continents save North America.  They appear to have evolved in Gondwana and spread.  They survived, as far as we can tell, last in what is now southern Africa. 

They varied in size from as small as about 3 1/2 inch Microgomphodon up to the estimated giant 3m (10 ft) long Megawhaitsia.  Most seemed to be around 1.5m (5 ft) long though, but later species were much smaller.

There were many clades

Lycosuchus

The earliest and basal most (sorta, most primitive) were the Lycosuchidae.  These "wolf crocodiles" were the earliest known therocephalians living during the Capitanian.  The most famous was, of course, Lycosuchus. While distinct, Lycosuchus has similar to the gorgonopsids.  However, one of the distinct features was the double canines.  There have been a lot of arguments over whether or not the double canines are a case of tooth replacement being seen in the fossil record, a defect in that particular animal or a true feature of the animal throughout its life.  Lycosuchus was fairly large, being 1.2m (almost 4 ft) long.  Simorhellia appears to be a close relative.

Pristeragnathus, a scylacosaurid

Scylacosaurus and its relatives in Scylacosauridae were the next most basal of the therocephalians.  Glanosuchus is one of the most famous of group and has the beginnings of many of the more advanced features that the therocephalians would develop in convergent evolution with the cynodonts and mammals.  Most of this group were large-ish carnivores being about 1.5 meters (5 ft) in length, roughly the length of a large wolf.

The remaining clade of the basal therocephalians is Trochosuchidae. These were similar to their cousins, the Scylacosauridae and Lycosuchidae. They lacked the crest on the skull of scylacosaurs, had a broader, more flatten skull and only had one, large canine tooth (yet for some reason many of the popular drawings have them with two.  odd that).

The True Beast Heads

Eutherocephalia, the "true beast heads" were the clade that could be described as more derived than the earlier, basal clades.  It was even more mammal like than its predecessors and is divided into several subclades as well: Akidnognathidae, Hofmeyriidae, Whaitsiidae, Baurioidea and others. We'll discuss, briefly, Akidnognathidae, Nanictidopidae, Whaitsiidae and Baurioidea.

Akidnognathidae is often the clade thought of if and when someone thinks of the therocephalians.  They encompassed the sabre toothed and much studied Moschorhinus and the famous Euchambersia, notable for being potentially venomous.  Moschorhinus is the most heavily studied of the group and survived the Permian Extinction.  After the extinction, it became smaller, demonstrating the so-called Lilliput Effect and developed even larger canines, becoming more sabre toothed than before.  Euchambersia was famous for being sorta portrayed in Walking with Beasts for having a poisonous bite.  That's controversial, to say the least, but it did have the grooves in its canines and a socket above for a poison gland consistent with venomous animals.  Akidnognathidae was fairly large, often about 1.5m (5 ft in length).  While members survived the Permian Extinction, most of its diversity was wiped out and it did not last long after.  In many ways Akidnognathidae appeared to be convergent with modern carnivores for its bauplans and niches.

Purlova, a nanictidopid therocephalian from Russia

Nanictidopidae is another clade of eutherocephalians.  They are notable for their distribution, found so far in South Africa and Russia, but also because they appear to be the first therocephalians to have become herbivores during the Late Permian.  They had reduced canines and tooth wear consistent with herbivory.  Their skulls were more robust and trianular than other eutherocephalains of their time and this has been suggested as support for herbivory as well.  Their skulls were about 20 cm in length and if their bauplan was consitent with other therocephalians, they were not small and had an overall length of 120 cm (4 ft).

Megawhaitsia, a highly speculative reconstruction of the whaitsiid therocephalian

Whaitsiidae is another notable clade within eutherocephalia.  They were general carnivores and around 1 meter in length.  Interestingly, they have 5 upper incisors and then 4 lower.  However, the most notable bit is one of its members (Megawhaitsia) is the largest therocephalian found to date: the maximilla found in Russia makes for an estimated skull length of up to 50 cm.  If the body plan follows that of other whaitsiids, then the body length is around 3 meters.  Since it lived during the time of the Gorgonopsids, it makes you wonder if they were locally absent for Megawhaitsia to become so large.

Bauria, the quintessential Bauroid

The last group of eutherocephalians I will be covering is the Baurioidea.  There is no way I can do any credit to this diverse and interesting group.  They tended to be small and they developed into near mammals.  Some were convergent with rodents (Bauria, Microgomphodon) and others started reconverging with the larger sabre toothed forms that had gone extinct (Nothogomphodon), but it might be better to call it a sabre-toothed badger.  They were herbivorous (Bauria et al) and carnivorous (Nothogomphodon).  They survived the Permian Extinction and even diversified during the disaster taxa stages, the earliest Triassic.  They were also the smallest therocephalians of any stripe: Microgomphodon was 9 cm (3.6 in) long.  The largest of them, Nothogomphodon, was around 50 cm long (20 inches).

Nothogomphodon, a bauroid therocephalian.

And that's all he wrote...

The therocephalians lasted for at least 20 million years.  Its likely we have not found the last of species they had, given there was a dicynodont recovered from the Australian Cretaceous, nor have we found the earliest of them either.  They had a good run.  However, for all their mad evolutionary innovation, it ought to be remembered, 20 million years from now in the past is in the Miocene Neogene for us.  Its a relative blink of time and yet they evolved and changed in some radical ways.  They were as big as short-faced bears to as small as a mouse.  They were aquatic like otters and were mini rodents and the amongst the largest of carnivores.  They were amazing in their own right.  Unfortunately, they are incredibly diverse and ought to have their own post like the dicynodonts and gorgonopsids for each of the clades given what we know, but, alas, I am a rocket scientist and ought to get back to that fun paperwork.

Ichibengops munyamadziensis: a new Eutherocephalian From Wuchiapingian Permian Zambia

A new eutherocephalian (Therapsida, Therocephalia) from the upper Permian Madumabisa Mudstone Formation (Luangwa Basin) of Zambia

Authors:

Huttenlocker et al

Abstract:

A new therocephalian therapsid, Ichibengops munyamadziensis, gen. et sp. nov., is described on the basis of two partial skulls from the upper Permian (Wuchiapingian) upper Madumabisa Mudstone Formation of the Luangwa Basin, Zambia. The specimens offer insights into the diversity of therocephalians in a poorly sampled region, preserving unique maxillary structures, dental morphology that is intermediate between basal therocephalians and eutherocephalians, and a maxillovomerine bridge forming an incipient secondary palate. A phylogenetic analysis of 135 craniodental and postcranial characters from 56 therapsid taxa (including 49 therocephalians) recovered I. munyamadziensis as the sister taxon of the Russian Chthonosaurus, with both taxa resolving near the hofmeyriid + whaitsiid + baurioid clade (either as the sister group to this clade or nested near whaitsiids). Ichibengops shares with Chthonosaurus several features, including a ventral maxillary flange in which the upper postcanines are situated (also in Lycosuchus), anteroposteriorly short suborbital vacuities with strongly scalloped anterior borders, a furrowed or ridged surface texture on the palatal surface of the palatine, and a possible maxillovomerine bridge (although this latter structure is incompletely preserved in Chthonosaurus). The new taxon, along with its proposed relationship to Chthonosaurus, adds to a list of sister-group pairs of Wuchiapingian tetrapods in southern Gondwana and Laurasia, indicating that effective, though largely unknown, dispersal routes persisted in Pangea at least through early late Permian times.

Simorhinella baini: Examining the Morphology of a Lycosuchid Therocephalian From Middle Permain South Africa

Adult morphology of the therocephalian Simorhinella baini from the middle Permian of South Africa and the taxonomy, paleobiogeography, and temporal distribution of the Lycosuchidae

Authors:

Abdala et al

Abstract:

The Middle Permian tetrapod fauna of the South African Beaufort Group is taxonomically diverse and includes representatives of all major therapsid groups, including the earliest records of Eutheriodontia. In the Middle Permian, eutheriodonts are represented mainly by large therocephalians, which made up a large proportion of the vertebrate predators in these faunas. Here we describe the skull and partial skeleton of a large therocephalian from the uppermost Tapinocephalus Assemblage Zone (AZ) of South Africa. A combination of features, including the short snout, presence of three to four upper postcanines and presence of teeth on the pterygoid processes, indicates that the new specimen belongs to the earliest-diverging therocephalian family, Lycosuchidae. The presence of a well-developed midline ridge on the ventral surface of the vomer indicates that the new specimen can be referred to Simorhinella baini, a species previously represented only by a tiny juvenile skull. The new specimen forms the basis for a taxonomic re-evaluation of the Lycosuchidae as well as of the geographic and stratigraphic range of the family. We recognize two valid species within the Lycosuchidae: the type species Lycosuchus vanderrieti represented by five specimens and Simorhinella baini represented by two specimens, with an additional 22 specimens currently identifiable as Lycosuchidae incertae sedis. Lycosuchid specimens range throughout the Tapinocephalus and Pristerognathus AZs; specimens of Simorhinella are restricted to the Tapinocephalus AZ, whereas Lycosuchus specimens are documented in both the Tapinocephalus and Pristerognathus AZs.

Tetrapods from Middle Triassic Antarctica

New Middle Triassic tetrapods from the upper Fremouw Formation of Antarctica and their depositional setting

Authors:

Sidor et al

Abstract:

Renewed field work in the Beardmore Glacier region of Antarctica has led to a new collection of tetrapod fossils from the upper member of the Fremouw Formation near Fremouw Peak. This locality records a sedimentary environment remarkably similar to that preserved at Gordon Valley, the only other locality known to preserve Cynognathus Assemblage Zone–equivalent taxa from Antarctica. Fossil bones are generally disarticulated and mixed with logs and reworked mudrock clasts, forming an intraformational channel-lag conglomerate. To date, very few bones of small-bodied taxa have been recovered from the upper Fremouw conglomerates, suggesting that they did not survive the reworking process. We use an apomorphy-based approach to record three previously unrecognized taxa from the upper Fremouw Formation: the dicynodont Angonisaurus, an indeterminate therocephalian therapsid, and an indeterminate crown-group archosaur. Combined with previous data, our work demonstrates that 10 distinct taxa can be recognized from the upper Fremouw, including two endemic temnospondyl species. Our recognition of Angonisaurus in the upper Fremouw Formation provides a new piece of evidence in favor of a correlation with the Cynognathus C subzone (uppermost Burgersdorp Formation) of South Africa and the Lifua Member of the Manda beds of Tanzania.

Observing the Lilliput Effects in Therocephalians Across the Permian Triassic Mass Extinction

Bone microstructure and the evolution of growth patterns in Permo-Triassic therocephalians (Amniota, Therapsida) of South Africa

Authors:

Huttenlocker et al

Abstract:

Therocephalians were a speciose clade of nonmammalian therapsids whose ecological diversity and survivorship of the end-Permian mass extinction offer the potential to investigate the evolution of growth patterns across the clade and their underlying influences on post-extinction body size reductions, or ‘Lilliput effects’. We present a phylogenetic survey of limb bone histology and growth patterns in therocephalians from the Middle Permian through Middle Triassic of the Karoo Basin, South Africa. Histologic sections were prepared from 80 limb bones representing 11 genera of therocephalians. Histologic indicators of skeletal growth, including cortical vascularity (%CV) and mean primary osteon diameters (POD), were evaluated in a phylogenetic framework and assessed for correlations with other biologically significant variables (e.g., size and robusticity). Changes in %CV and POD correlated strongly with evolutionary changes in body size (i.e., smaller-bodied descendants tended to have lower %CV than their larger-bodied ancestors across the tree). Bone wall thickness tended to be high in early therocephalians and lower in the gracile-limbed baurioids, but showed no general correlation with cross-sectional area or degree of vascularity (and, thus, growth). Clade-level patterns, however, deviated from previously studied within-lineage patterns. For example, Moschorhinus, one of few therapsid genera to have survived the extinction boundary, demonstrated higher %CV in the Triassic than in the Permian despite its smaller size in the extinction aftermath. Results support a synergistic model of size reductions for Triassic therocephalians, influenced both by within-lineage heterochronic shifts in survivor taxa (as reported in Moschorhinus and the dicynodont Lystrosaurus) and phylogenetically inferred survival of small-bodied taxa that had evolved short growth durations (e.g., baurioids). These findings mirror the multi-causal Lilliput patterns described in marine faunas, but contrast with skeletochronologic studies that suggest slow, prolonged shell secretion over several years in marine benthos. Applications of phylogenetic comparative methods to new histologic data will continue to improve our understanding of the evolutionary dynamics of growth and body size shifts during mass extinctions and recoveries.

Capitanian Permian Pareiasaur Parareptiles, Herbivorous Dinocephalian Therapsids Were Not Competitors

Insights into the habitat of Middle Permian pareiasaurs (Parareptilia) from preliminary isotopic analyses

Authors:

Canoville et al

Abstract:

Pareiasaurs were an abundant group of large herbivores during Middle and Late Permian times. The habitat of pareiasaurs has proven enigmatic, and ecological interpretations from anatomical and taphonomic data have included aquatic, semi-aquatic to fully terrestrial lifestyles. Insight into the ecology of extinct taxa can also be gained from stable isotope analyses, and interpretations benefit from studies of multiple, coeval groups. Here, we report the first stable carbon and oxygen isotope analyses from the enamel, dentine and bone of pareiasaurs and contemporaneous therapsids (dinocephalians and therocephalians), in specimens recovered from the Permian Tapinocephalus to lower Pristerognathus Assemblage Zones of South Africa. Previous ecological inferences for dinocephalians (riparian to terrestrial) and therocephalians (terrestrial) are less ambiguous than reconstructions for pareiasaurs and provide an independent reference for interpreting stable isotope measurements. Oxygen isotopes of enamel carbonate were indistinguishable between pareiasaurs and therocephalians, which had higher values than dinocephalians. The data suggest that dinocephalians and pareiasaurs (megaherbivores) inhabited different ecological niches and that pareiasaurs may have shared a terrestrial habitat with therocephalians (carnivores). Our results agree with earlier suggestions of a terrestrial lifestyle among pareiasaurs and provide evidence of niche partitioning among large coeval Capitanian herbivores of South Africa.

Just a Quick Note on Therocephalia

It seems like akidnognathanidae was trying really hard to be the therocephalian equivalent of carnivora and bauriodea was trying to be rodentia.

Parallel evolution and all that.

Interesting.

In Prep For the Therocephalian Post

via Huttenlocker.