Tapinocephalidae

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Tapinocephalidae
Temporal range: Middle Permian, 268–260  Ma
Moschops capensis - AMNH - DSC06321.JPG
Mounted skeleton of Moschops capensis. The skeleton is displayed at the American Museum of Natural History
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Suborder: Dinocephalia
Infraorder: Tapinocephalia
Family: Tapinocephalidae
Lydekker, 1890
Subgroups

Tapinocephalidae is an extinct family of advanced tapinocephalians. It is defined as the clade containing Ulemosaurus , Tapinocaninus , and the Tapinocephalinae. [1] They are known from both Russia and South Africa. In all probability, the Tapinocephalidae had a worldwide (Pangean) distribution. They flourished briefly during the Wordian and Capitanian ages, radiating into several lineages, existing simultaneously, and differing mainly in details of the skull and, to an even lesser degree, the skeleton. It is not clear how such similar animals could each find their own ecological niche, but such was obviously the case. There is a parallel here with the hadrosaur and ceratopsian dinosaurs of the Late Cretaceous. The cause of their abrupt extinction is not clear, since other smaller animals, and even the pareiasaurs, were not affected. Quite probably, like the extinction of the late Pleistocene megafauna, a number of factors were involved.

Contents

Description

Restoration of Ulemosaurus Ulemosaurus22DB.jpg
Restoration of Ulemosaurus

The body is deep and capacious, allowing for a developed herbivore gut. The shoulders are much higher than the pelvic region, so that the back slopes, giraffe-fashion, from neck to tail. This seems to imply that they fed on vegetation of about a meter or more from the ground. The limbs are heavy, with sturdy forelegs that sprawled out to the sides, while the longer hind legs were placed directly under the hips (the dicynodonts had the same posture). The feet are broad and short.

Skull

Skull of Moschops capensis Tapinocephalidae - Moschops capensis.JPG
Skull of Moschops capensis

The tapinocephalid skull is massively constructed, and either long-snouted (e.g. Struthiocephalus ) or high and short (e.g. Moschops ). Very often the top of the head is rounded, and the bones of the forehead are elevated into a sort of dome or boss, in the middle of which is a large pineal opening. In some specimens this boss is of only moderate thickness, while in others it has become greatly thickened into a huge mass of bone (pachyostosis). It has been suggested that these animals engaged in intra-specific head-butting behavior, presumably for territory or mates. A similar thickening of the skull occurs in pachycephalosaurian ("boneheaded") dinosaurs, and it is speculated that all of these animals practiced head-butting behavior like modern goats and bighorn sheep, or Late Eocene titanotheres.

In keeping with their vegetarian lifestyle, the chisel-edged teeth are undifferentiated, lacking canines, and rather peg-like. In maturity the teeth have a talon and a crushing heel and the upper and lower teeth of the whole battery intermesh.

Size

The tapinocephalids were an advanced family of giant herbivorous dinocephalians, with an adult weight from about 500 to 1,000 kilograms (1,100 to 2,200 lb), possibly up to 1.5 or 2 tonnes (3,310 or 4,410 lb) in the largest forms, such as Tapinocephalus atherstonei. The trend towards gigantism, so typical of many of the dinocephalians, was characteristic of even the earliest known members of this family. Along with pareiasaurs, these were the heavyweights of the middle Permian.

Palaeobiology

Head-butting behaviour of Tapinocephalus Tapinocephalus DB.jpg
Head-butting behaviour of Tapinocephalus

Ecology

There is some disagreement over whether these animals lived in dry upland environments (Colbert), swamps, or either, depending on the species or tribe. There is no doubt that the Tapinocephalidae occupied different ecological niches. However, the tendency of earlier writers like Gregory (1926) and Boonstra (1965) to consider them semi-aquatic wallowers is reminiscent of the old fable of the sauropods consigned to the swamps because their limbs were too clumsy and their bodies too heavy for them to exist on dry land. [2] [3] In fact, if they were head-butters, it is unlikely they could have been clumsy swamp wallowers, since head-butting implies some degree of mobility.

Boonstra suggests that form such as Tapinocephalus and Struthiocephalus were semi-aquatic, while Moschops was terrestrial. It is quite likely that some tapinocephalid species may have frequented pond margins, feeding on soft vegetation, others preferred dry uplands.

Gregory (1926) considered that dinocephalians were aquatic animals, the wide hands and feet and the extensive fore and aft reach being useful for propelling the animal through water and the massive forehead being an advantage in diving. He suggested that the pineal organ might have been phototropic, helping the animal to orient itself relative to the surface of the water. [2]

Tapinocephalines were seen by Boonstra (1956) as semi-aquatic animals. The cumbersome body, poor locomotor apparatus and feeble lower jaw and massive cranium all suggested to him that these animals could not have fed efficiently on land on tough vegetation. Instead he presented them as wallowers, being buoyed up by water, feeding on soft marsh vegetation. [4]

Physiology

Rescuing the tapinocephalids from a life of diluvian swamp-wallowing, Bakker (1975, 1986) argued that bone histology, geographic distribution, and predator-prey relationships showed that these were active, fully terrestrial and at least partially endothermic animals, midway between the ectothermic pelycosaurs and the fully endothermic theriodonts. [5] [6]

Others like McNab and Geist suggest that the tapinocephalids were better considered inertial homeotherms, with the large barrel-like body and short tail being the most efficient surface for conserving heat.

Related Research Articles

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Dinocephalians are a clade of large-bodied early therapsids that flourished in the Early and Middle Permian between 279.5 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalians were the first non-mammalian therapsids to be scientifically described and their fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania.

<i>Bradysaurus</i> Extinct genus of reptiles

Bradysaurus was a large, early and common pareiasaur. They possessed a covering of armoured scutes, likely serving as defense against their main predators, the gorgonopsians.

<i>Moschops</i> Extinct genus of therapsids that lived in the Guadalupian epoch

Moschops is an extinct genus of therapsids that lived in the Guadalupian epoch, around 265–260 million years ago. They were heavily built plant eaters, and they may have lived partly in water, as hippopotamuses do. They had short, thick heads and might have competed by head-butting each other. Their elbow joints allowed them to walk with a more mammal-like gait rather than crawling. Their remains were found in the Karoo region of South Africa, belonging to the Tapinocephalus Assemblage Zone. Therapsids, such as Moschops, are synapsids, the dominant land animals in the Permian period, which ended 252 million years ago.

<i>Tapinocephalus</i> Extinct genus of therapsids

Tapinocephalus is an extinct genus of large herbivorous dinocephalians that lived during the Middle Permian Period in what is now South Africa. Only the type species, Tapinocephalus atherstonei is now considered valid for this genus.

<i>Deuterosaurus</i> Extinct genus of therapsids

Deuterosaurus is an extinct genus of dinocephalian therapsids, one of the non-mammalian synapsids dominating the land during the late Paleozoic.

<i>Ulemosaurus</i> Extinct genus of therapsids

Ulemosaurus is an extinct genus of dinocephalian therapsids that lived 265 to 260 million years ago, at Isheevo in Russian Tatarstan. It was a tapinocephalid, a group of bulky herbivores which flourished in the Middle Permian. Ulemosaurus and other tapinocephalians disappeared at the end of the Middle Permian.

<span class="mw-page-title-main">Anteosaur</span> Extinct clade of therapsids

Anteosaurs are a group of large, primitive carnivorous dinocephalian therapsids with large canines and incisors and short limbs, that are known from the Middle Permian of South Africa, Russia, China, and Brazil. Some grew very large, with skulls 50–80 centimetres (20–31 in) long, and were the largest predators of their time. They died out at the end of the Middle Permian, possibly as a result of the extinction of the herbivorous Tapinocephalia on which they may have fed.

<span class="mw-page-title-main">Tapinocephalia</span> Extinct clade of therapsids

The Tapinocephalia are one of the major groups of dinocephalian therapsids and the major herbivorous group. Tapinocephalia has been found to consist of three clades: Styracocephalidae, Titanosuchidae, and the very successful Tapinocephalidae. Notable tapinocephalians include Moschops, Tapinocephalus, and Titanosuchus.

<span class="mw-page-title-main">Titanosuchidae</span> Extinct family of therapsids

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<i>Elginia</i> Extinct genus of reptiles

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<i>Anteosaurus</i> Extinct genus of anteosaurid synapsid from the Permian

Anteosaurus is an extinct genus of large carnivorous dinocephalian synapsid. It lived at the end of the Guadalupian during the Capitanian stage, about 265 to 260 million years ago in what is now South Africa. It is mainly known by cranial remains and few postcranial bones. Measuring 5–6 m (16–20 ft) long and weighing about 600 kg (1,300 lb), Anteosaurus was the largest known carnivorous non-mammalian synapsid and the largest terrestrial predator of the Permian period. Occupying the top of the food chain in the Middle Permian, its skull, jaws and teeth show adaptations to capture large prey like the giants titanosuchids and tapinocephalids dinocephalians and large pareiasaurs.

<i>Tapinocephalus</i> Assemblage Zone

The Tapinocephalus Assemblage Zone is a tetrapod assemblage zone or biozone which correlates to the middle Abrahamskraal Formation, Adelaide Subgroup of the Beaufort Group, a fossiliferous and geologically important geological Group of the Karoo Supergroup in South Africa. The thickest outcrops, reaching approximately 2,000 metres (6,600 ft), occur from Merweville and Leeu-Gamka in its southernmost exposures, from Sutherland through to Beaufort West where outcrops start to only be found in the south-east, north of Oudshoorn and Willowmore, reaching up to areas south of Graaff-Reinet. Its northernmost exposures occur around the towns Fraserburg and Victoria West. The Tapinocephalus Assemblage Zone is the second biozone of the Beaufort Group.

<i>Struthiocephalus</i> Extinct genus of therapsids

Struthiocephalus is an extinct genus of dinocephalian therapsids from the Permian of South Africa. It was a large animal, reaching 288 kg (635 lb) in body mass.

<i>Tapinocaninus</i> Extinct genus of therapsids

Tapinocaninus is an extinct genus of therapsids in the family Tapinocephalidae, of which it is the most basal member. Only one species is known, Tapinocaninus pamelae. The species is named in honor of Rubidge's mother, Pam. Fossils have been found dating from the Middle Permian.

<i>Styracocephalus</i>

Styracocephalus platyrhynchus (Greek for "spiked-head") is an extinct genus of dinocephalian therapsid that existed during the mid-Permian throughout South Africa, but mainly in the Karoo Basin. It is often referred to by its single known species Styracocephalus platyrhynchus. The Dinocephalia clade consisted of the largest land vertebrates and herbivores during the early to mid-Permian. This period is often also referred to as the Guadalupian epoch, approximately 270 to 260 million years ago.

<i>Moschognathus</i> Extinct genus of therapsids that lived in the Guadalupian epoch

Moschognathus is an extinct genus of dinocephalian therapsid in the family Tapinocephalidae. The genus includes only the type species M. whaitsi, named by palaeontologist Robert Broom in 1914. It was a short-snouted tapinocephalid, closely related to and resembling the well-known genus Moschops, but its skull is less thickened overall has a relatively longer and shallower snout by comparison. Indeed, Moschognathus has typically been regarded as a junior synonym of Moschops since 1969 after Lieuwe Dirk Boonstra sunk Moschognathus into Moschops, albeit retained as its own doubtfully valid species. However, researchers in the 21st century have expressed doubt over this synonymy and suggested that Moschognathus is a distinct taxon after all, including first by Christian Kammerer in a 2009 Ph.D. thesis and formally in 2015 by Alessandra D. S. Boos and colleagues in 2015. Moschognathus has since began to re-enter scientific literature of dinocephalians as a valid name and treated distinct from Moschops.

<i>Criocephalosaurus</i> Extinct genus of therapsids

Criocephalosaurus is an extinct genus of tapinocephalian therapsids that lived in Southern Africa during the Guadalupian epoch of the Permian. They are the latest surviving dinocephalians, extending past the Abrahamskraal Formation into the lowermost Poortjie Member of the Teekloof Formation in South Africa. They are also regarded as the most derived of the dinocephalians, alongside Tapinocephalus, and the most abundant in the fossil record.

<i>Pampaphoneus</i> Extinct genus of therapsids

Pampaphoneus is an extinct genus of carnivorous dinocephalian therapsid belonging to the family Anteosauridae. It lived 268 to 265 million years ago during the Wordian age of the Guadalupian period in what is now Brazil. Pampaphoneus is known by an almost complete skull with the lower jaw still articulated, discovered on the lands of the Boqueirão Farm, near the city of São Gabriel, in the state of Rio Grande do Sul. A second specimen from the same locality was reported in 2019 and 2020 but has not yet been described. It is composed of a skull associated with postcranial remains. It is the first South American species of dinocephalian to have been described. The group was previously known in South America only by a few isolated teeth and a jaw fragment reported in 2000 in the same region of Brazil. Phylogenetic analysis conducted by Cisneros and colleagues reveals that Pampaphoneus is closely related to anteosaurs from European Russia, indicating a closer faunal relationship between South America and Eastern Europe than previously thought, thus promoting a Pangea B continental reconstruction.

Parasumina is an extinct genus of anomodont known from the late Capitanian age at the end of the middle Permian period of European Russia. The type and only species is Parasuminia ivakhnenkoi. It was closely related to Suminia, another Russian anomodont, and was named for its resemblance. Little is known about Parasuminia as the only fossils are of fragmentary pieces of the skull and jaw, but the known remains suggest that its head and jaws were deeper and more robust than those of Suminia, and with shorter, stouter teeth. However, despite these differences they appear to have been similar animals with a similarly complex method of processing vegetation.

References

  1. "†Tapinocephalia".
  2. 1 2 The skeleton of Moschops capensis Broom, a dinocephalian reptile from the Permian of South Africa. Gregory, WT. 1926. pp. 179–251.
  3. The skull of Struthiocephalus kitchingi. Boonstra, LD. 1965. pp. 251–265.
  4. The skull of Tapinocephalus and its near relatives. Boonstra, LD. 1956. pp. 137–169.
  5. Bakker, RT (1975). "Dinosaur Renaissance". Scientific American. 232 (4): 58. Bibcode:1975SciAm.232d..58B. doi:10.1038/scientificamerican0475-58.
  6. Bakker, RT (August 1986). "The Dinosaur Heresies : New Theories Unlocking the Mystery of the Dinosaurs and Their Extinction". Wm. Morrow & Co. (Reissue edition).