Peltocephalus maturin Temporal range: Late Pleistocene - Early Holocene | |
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The holotype mandible of P. maturin seen from three different angles. | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Testudines |
Suborder: | Pleurodira |
Family: | Podocnemididae |
Genus: | Peltocephalus |
Species: | †P. maturin |
Binomial name | |
†Peltocephalus maturin Ferreira et al., 2024 [1] | |
Peltocephalus maturin is an extinct species of podocnemidid river turtle closely related to the big-headed Amazon River turtle (Peltocephalus dumerilianus) that lived during the Late Pleistocene and Early Holocene in what is now Brazil. P. maturin is known from a singular lower jaw of enormous size, with estimates suggesting its carapace may have reached lengths of around 1.70 m (5 ft 7 in). This would make it one of the largest freshwater turtles in history, comparable in size to the Paleocene podocnemidid Carbonemys and only exceeded by the Miocene podocnemidid Stupendemys . Like its closest relative, it was likely an omnivore, the narrow cutting surface of its lower jaw unsuited for strict herbivory or durophagy.
Peltocephalus maturin was described in 2024 on the basis of specimen MERO.PV.H 007, a partial lower jaw discovered by gold miners within the Taquaras Quarry of Rondônia, Brazil. Since the Rio Madeira Formation is the only geological unit exposed at this quarry, the fossil is subsequently assumed to be Late Pleistocene to Early Holocene in age. [1]
The species name references Maturin, a recurring entity in the works of Stephen King said to be a giant turtle that created the universe. King in turn derived the name from the character of Stephen Maturin from the novel H.M.S. Surprise, in which he names a giant tortoise. [1] [2]
Although the type material of Peltocephalus maturin is restricted to an incomplete mandible, a lot of information has been derived from this material. The mandibular symphysis are fused, clearly placing the animal within Pelomedusoides. The labial and lingual ridges, which are located to either side of the triturating (cutting or grinding) surface of the lower jaw, are straight, which sets them apart from the curved ridges seen in species of Podocnemis , the South American river turtles. It further differs from species of that genus by having a U-shaped outline of the midline of the lingual ridges and a lingual platform that is located towards the back on the mandible, ventrally (below) to the triturating surface and the symphyseal fossa. This fossa contains two pits, which can be used to differentiate the mandible of Peltocephalus maturin from the extant Madagascan big-headed turtle of the genus Erymnochelys . Impressions left by the rhamphotheca, the outermost keratinous layer of the beak, indicate that its back edge sloped dorsoventrally (from the top to the bottom of the jaw), whereas in both Podocnemis and Erymnochelys it slopes posteroventrally, meaning both down and towards the back of the jaw. A striking feature of Peltocephalus maturin is the greatly enlarged symphyseal hook that is formed at the tip of the lower jaw. The fact that this hook ends above the coronoid process, together with the lingual platform and the presence of two pits located within the symphyseal fossa, clearly identify it as a relative of the Big-headed Amazon River turtle, thus its placement within the genus Peltocephalus. [1]
In addition to size, Peltocephalus maturin can be differentiated from its modern relative by the fact that the labial ridge that stretches closer to the outer surface of the dentary is higher up than the lingual (inner) ridge. Also unlike its modern relative, the two triturating surfaces enclosed by these ridges do not meet in the middle, as they are separated by a symphyseal ridge that stretches along the midline of the dentary. Additionally, each triturating surface can be divided into an anterior and posterior section, divided by a secondary ridge that runs at a right angle to the triturating surface. Ferreira and colleagues note that these features except for the presence of a secondary ridge are also shared by the enormous Miocene Stupendemys . However, Stupendemys and Peltocephalus maturin differ in that the latter has a more upturned symphyseal hook, narrower triturating surfaces and by having lower lingual ridges that from a V-shape towards the tip of the mandible, rather than the protruding ridges in Stupendemys that form a U-shape. [1]
One of the most notable things about Peltocephalus maturin is the size of the holotype mandible. The dentary measures 27.8 cm (10.9 in) in length, which is comparable to that of the Cretaceous marine turtle Archelon . Total length estimates were conducted through two approaches, both yielding similar results. Approach 1 suggests an estimated straight carapace length of approximately 1.70 m (5 ft 7 in) while approach 2 yielded a slightly longer 1.73 m (5 ft 8 in). The lower and upper bounds lie between approximately 1.40–2.16 m (4 ft 7 in – 7 ft 1 in). While this would put the total length of Peltocephalus maturin below those of giants like Archelon and Stupendemys, it would still be one of the largest freshwater turtles in terms of carapace length, matched only by Carbonemys (estimated straight carapace length 1.8 m (5 ft 11 in)). It also far exceeds any other freshwater turtle of the Quaternary such as the Asian narrow-headed softshell turtle (straight carapace length 1.40 m (4 ft 7 in)) and the Arrau turtle (straight carapace length 1.09 m (3 ft 7 in)). [1] [3]
Phylogenetic analysis confirmed the relationship between Peltocephalus maturin and Peltocephalus dumerilianus, both of which forming a clade that is deeply nested within Podocnemididae. The levels of resolution do differ between the two analysis conducted, with the strict consensus being poorly resolved though still supporting the clade formed by the two Peltocephalus species. The Majority Rule Tree, depicted below, yielded better resolved results that are in line with the internal relationships that were recovered by previous studies. Within this tree, Peltocephalus species are the basalmost off-shoot of a branch that also includes Stupendemys and the various species of Bairdemys, together forming one of two distinct branches within Erymnochelyinae. [1]
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Diet in turtles can generally be inferred based on the height of the skull as well as the proportions and complexity of the triturating surface, which is used to cut and grind food. In this regard, Peltocephalus maturin bears close resemblance to its modern relative. Overall, podocnemidids are omnivores that consume varying levels of plant material, with Peltocephalus dumerilianus incorporating the greatest amount of other animals into its diet including apple snails. This is expressed through a much more simple triturating surface than what is seen in more herbivorous podocnemidids. The narrow triturating surface of Peltocephalus maturin is not especially well suited for durophagy nor herbivory, however at the same time the midline ridge that separates the triturating surfaces from another does suggest slightly less carnivorous habits than those of P. dumerilianus. [1]
The great size of this species might have been a factor that allowed it to fill a different nische from other podocnemidids, something that has been a proposed factor in the coexistence of the large-bodied Caninemys and Stupendemys during the Miocene and could also be responsible for the coexistence of today's Amazonian podocnemidids. The evolution of such a large bodysize further matches certain patterns within reptile evolutions, with prior size increases being noted to have taken place during the Paleogene in podocnemidids and snakes (like Titanoboa ) as well as during the Miocene with podocnemidids and crocodilians (like Purussaurus ). The discovery of Peltocephalus maturin matches the great size seen in certain Quaternary squamates like the varanid megalania (Varanus priscus), the teiid Tupinambis uruguaianensis , and the madtsoiid Wonambi . Other testudines reached massive sizes during this time as well, such as Megalochelys atlas . [1]
Ferreira and colleagues speculate that the extinction of Peltocephalus maturin may have been tied to exploitation by humans. Part of their reasoning is based on the extinction of various island species such as the turtles of the Turks and Caicos Islands as well as the meiolanids of Vanuatu and New Caledonia which are often thought to have been driven to extinction by human overhunting. Some of the earliest evidence for humans arriving in South America dates to roughly 12.6 to 9.8 thousand years BP and thus overlap with the presence of Peltocephalus maturin. Furthermore, sites that show signs of human habitation also preserve the remains of both tortoises and podocnemidids, with even modern humans still hunting turtles for their meat. At the same time, there is no evidence that humans and Peltocephalus maturin ever actually met, meaning that the reason for this species' extinction remains uncertain until the discovery of better materials provides more clues. [1]
Podocnemididae is a family of pleurodire (side-necked) turtles, once widely distributed. Most of its 41 genera and 57 species are now extinct. Seven of its eight surviving species are native to South America: the genus Peltocephalus, with two species, only one of which is extant ; and the genus Podocnemis, with six living species of South American side-necked river turtles and four extinct. There is also one genus native to Madagascar: Erymnochelys, the Madagascan big-headed turtle, whose single species E. madagascariensis.
Archelon is an extinct marine turtle from the Late Cretaceous, and is the largest turtle ever to have been documented, with the biggest specimen measuring 4.6 m (15 ft) from head to tail and 2.2–3.2 t in body mass. It is known only from the Pierre Shale and has one species, A. ischyros. In the past, the genus also contained A. marshii and A. copei, though these have been reassigned to Protostega and Kansastega, respectively. The genus was named in 1895 by American paleontologist George Reber Wieland based on a skeleton from South Dakota, who placed it into the extinct family Protostegidae. The leatherback sea turtle was once thought to be its closest living relative, but now, Protostegidae is thought to be a completely separate lineage from any living sea turtle.
Macroplata is an extinct genus of Early Jurassic rhomaleosaurid plesiosaur which grew up to 4.65 metres (15.3 ft) in length. Like other plesiosaurs, Macroplata probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful forward stroke for fast swimming. Macroplata also had a relatively long neck, twice the length of the skull, in contrast to pliosaurs.
Stupendemys is an extinct genus of freshwater side-necked turtle, belonging to the family Podocnemididae. It is the largest freshwater turtle known to have existed, with a carapace over 2 meters long. Its fossils have been found in northern South America, in rocks dating from the Middle Miocene to the very start of the Pliocene, about 13 to 5 million years ago. Male specimens are known to have possessed bony horns growing from the front edges of the shell and the discovery of the fossil of a young adult shows that the carapace of these turtles flattens with age. A fossil skull described in 2021 indicates that Stupendemys was a generalist feeder.
Pliosaurus is an extinct genus of thalassophonean pliosaurid known from the Late Jurassic of Europe and South America. Most European species of Pliosaurus measured around 8 metres (26 ft) long and weighed about 5 metric tons, but P. rossicus and P. funkei would have been one of the largest plesiosaurs of all time, exceeding 10 metres (33 ft) in length. This genus has contained many species in the past but recent reviews found only six to be valid, while the validity of two additional species awaits a petition to the International Code of Zoological Nomenclature. Currently, P. brachyspondylus and P. macromerus are considered dubious, while P. portentificus is considered undiagnostic. Species of this genus are differentiated from other pliosaurids based on seven autapomorphies, including teeth that are triangular in cross section. Their diet would have included fish, cephalopods, and marine reptiles.
Kambara is an extinct genus of mekosuchine crocodylian that lived during the Eocene epoch in Australia. It is generally thought to have been a semi-aquatic generalist, living a lifestyle similar to many of today's crocodiles. Four species are currently recognised, the sympatric Kambara murgonensis and Kambara implexidens from sediments near Murgon, the poorly preserved Kambara molnari from the Rundle Formation and the youngest of the four, Kambara taraina, also from the Rundle Formation. Kambara were medium-sized crocodilians, with mature specimens generally reaching lengths from 3–4 m (9.8–13.1 ft).
The Big-headed Amazon River turtle, also known as the big-headed sideneck, is a species of turtle in the family Podocnemididae. An additional, much larger species is known, the extinct Peltocephalus maturin, is also part of the genus, Peltocephalus.
Laganosuchus is an extinct genus of stomatosuchid crocodyliform. Fossils have been found from Niger and Morocco and date back to the Upper Cretaceous.
Carbonemys cofrinii is an extinct giant podocnemidid turtle known from the Middle Paleocene Cerrejón Formation of the Cesar-Ranchería Basin in northeastern Colombia. The formation is dated at around 60 to 57 million years ago, starting at about five million years after the KT extinction event.
Globidentosuchus is an extinct genus of basal caimanine crocodylian known from the late Middle to Late Miocene of the Middle and the Upper Members of the Urumaco Formation at Urumaco, Venezuela. Its skull was very short and robust, with large units of spherical teeth used to break the shells of molluscs as part of its durophagus diet. It is thought to be one of the most basal Caimanines, even sharing some traits with alligatorids.
Khunnuchelys was a genus of trionychine turtle from the Late Cretaceous of Asia. Three species are known, K. erinhotensis, the type species, K. kizylkumensis, and K. lophorhothon. K. erinhotensis is known from the Iren Dabasu Formation in China from the late Turonian until the middle Campanian. K. kizylkumensis is known from the late Turonian Bissekty Formation of Uzbekistan. The third species, described in 2013 by Danilov et al., is known from the early to middle Campanian aged Bostobe Formation of Kazakhstan.
Megalochelys is an extinct genus of tortoises that lived from the Miocene to Pleistocene. They are noted for their giant size, which is among the largest of any known testudine, with a maximum carapace length over 2 m (6.5 ft) in M. atlas. During the dry glacial periods it ranged from western India and Pakistan to as far east as Sulawesi and Timor in Indonesia, though the island specimens likely represent distinct species.
Basilemys is a large, terrestrial nanhsiungchelyid turtle from the Upper Cretaceous of North and Central America. Basilemys has been found in rocks dating to the Campanian and Maastrichtian subdivisions of the Late Cretaceous and is considered to be the largest terrestrial turtle of its time. In an analysis made by Sukhanov et al. on a nansiunghelyid turtle from the Upper Cretaceous of Mongolia, it was demonstrated that Asian nanhsiungchelyids gave rise to the North American nanhsiungchelyids.
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Caiman brevirostris is an extinct species of caiman that lived during the Late Miocene, around 11.6 million years ago, to the end of the Miocene 5.3 million years ago in Acre and Amazonas, Brazil as well as Urumaco, Venezuela. Several specimens have been referred to the species, but only 3 of them are confidently placed in the species. C. brevirostris was originally named in 1987 on the basis of a single, incomplete rostrum with an associated mandibular ramus that had been found in Acre, Brazil. C. brevirostris is very distinct among Caiman species and caimaninae overall in that it preserves a characteristically short and robust skull that bears blunt posterior teeth that were built to break down harder foods. This was an adaption for durophagy, likely to crush shells of mollusks and clams which were common in the wetlands that C. brevirostris resided in.
Caninemys is an extinct genus of large freshwater side-necked turtle, belonging to the family Podocnemididae. Its fossils have been found in Brazil and Colombia, in rocks dating back from the middle to late Miocene.
Kyhytysuka is an extinct genus of ophthalmosaurian ichthyosaur from Early Cretaceous Colombia. The animal was previously assigned to the genus Platypterygius, but given its own genus in 2021. Kyhytysuka was a mid-sized ophthalmosaurian with heterodont dentition and several adaptations suggesting that it was a macropredatory vertebrate hunter living in shallow waters. It contains a single species, Kyhytysuka sachicarum.
Drazinderetes is a large bodied genus of soft shell turtle from the Middle Eocene Drazinda Formation of Pakistan. Its presence in the shallow marine deposits of the Drazinda Formation suggests that Drazinderetes may have been a partially or fully marine animal. Indetermined trionychine remains from the same formation may suggest that Drazinderetes could have been among the largest known turtles, with one entoplastron indicating a potential length of 1.5 to 2.1 meters. Drazinderetes currently consists of only a single species: Drazinderetes tethyensis.
Pachagnathus is an extinct genus of non-pterodactyloid pterosaur from the late Norian–early Rhaetian-aged Quebrada del Barro Formation of Argentina. It lived in the Late Triassic period, and is one of the only known definitive Triassic pterosaurs from the southern hemisphere. It is also one of the few known continental Triassic pterosaurs, indicating that the absence of early pterosaurs in both the southern hemisphere and terrestrial environments is likely a sampling bias, and not a true absence.
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