Amabilis uchoensis

Amabilis uchoensis is a species of prehistoric pleurodiran turtle from the Late Cretaceous of South America. It is the only species in the genus Amabilis.

Amabilis uchoensis Temporal range: Santonian ~86.3–83.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Amabilis uchoensis skull CT scan in dorsal (top left), ventral (top right), right lateral (centre left), anterior (centre right), left lateral (bottom left) and posterior (bottom right) views
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Pleurodira
Hyperfamily:	Pelomedusoides
Clade:	Podocnemidoidae
Genus:	†Amabilis Hermanson et al., 2020
Species:	†A. uchoensis
Binomial name
†Amabilis uchoensis Hermanson et al., 2020

Description

Hermanson et al. (2020) described the Late Cretaceous turtle Amabilis uchoensis based on a single partial skull from the São José do Rio Preto Formation, in the Brazilian state of São Paulo. The São José do Rio Preto Formation is thought to have been deposited during the Santonian age of the Late Cretaceous, between 86.3 and 83.6 million years ago.^[1]

The type-specimen skull, which is 2.25 cm long and 2.06 cm wide, suggests that the animal was smaller than any other fossil turtles found in Brazil's Bauru Group.^[2] Modern Brazilian river turtles are also considerably larger, ranging in length from 34 cm (Podocnemis erythrocephala) to 90 cm (Podocnemis expansa.)^[3] This skull is deposited in Uchoa's Museum of Paleontology.^[2]

The fossil is in the suborder Pleurodira, also known as "side-necked turtles" because their defensive posture hides the head under the shell by pulling the head to one side, rather than by withdrawing the head directly back under the shell.^[4]

The Amabilis genus is part of the superfamily or pan-group Podocnemidoidae, which groups the family Podocnemididae together with some related extinct genera, as well as the extinct family Peiropemydidae.^[5] Podocnemidoids, first seen in the Late Cretaceous, were once widely distributed across "North and South America, Europe, Asia, and Africa," according to Gaffney et al. (2011.)^[6] No surviving turtle species descend directly from Amabilis, which is therefore considered to be a stem group within its family and super-family. Because it is a member of Podocnemidoidae but not a member of the Podocnemididae. Hermanson et al. describe it as "a non-podocnemidid member of Podocnemidoidae."^[2]

According to the local newspaper Diário da Região, A. uchoensis was the first fossil turtle found in the São José do Rio Preto region (near the city of São Paulo). The turtle skull fragment was found by Brazilian paleontologist Fabiano Vidoi Iori, very near to the 2014 discovery site of carnivorous dinosaur Thanos simonattoi.^[7]

Name

The name Amabilis, according to Hermanson et al., is from the "Latin for 'lovable', for its tiny size."^[2]

References

1. Costa Menegazzoa, Mirian; Catuneanu, Octavian; Chang, Hung Kiang (2016). "The South American retroarc foreland system: The development of the Bauru Basin in the back-bulge province". Marine and Petroleum Geology. 73: 131–156. Bibcode:2016MarPG..73..131M. doi:10.1016/j.marpetgeo.2016.02.027. hdl:11449/165168. S2CID 130810296. Retrieved November 28, 2021. The age of the São José do Rio Preto Formation is estimated as Santonian, considering its stratigraphic relationship, i.e., partially correlated with the Araçatuba and Adamantina formations and overlying the Santo Anastácio Formation as well as the association of 'P.' brasiliensis, Megaraptora, I. bauruensis, I. wichmanni and isolated teeth of crocodyliformes.
2. Hermanson, Guilherme; Iori, Fabiano V.; Evers, Serjoscha W.; Langer, Max C.; Ferreira, Gabriel S. (2020). "A small podocnemidoid (Pleurodira, Pelomedusoides) from the Late Cretaceous of Brazil, and the innervation and carotid circulation of side-necked turtles". Papers in Palaeontology. 6 (2): 329–347. Bibcode:2020PPal....6..329H. doi:10.1002/spp2.1300. ISSN 2056-2802. A particularly large number of fossil pleurodires, many belonging to the Podocnemidoidae, has been recovered from the Upper Cretaceous Bauru Group outcrops of south-central Brazil...Amabilis differs from all other Podocnemidoidae in possessing a medially open fenestra postotica and lacking a basioccipital–opisthotic contact (also absent only in Mogharemys blanckenhorni).
3. "Amazonian turtles". Wildlife Conservation Society Brazil. Retrieved November 30, 2021. WCS-Brazil decided to focus on conservation of Amazonian river turtles, especially the five species of the Podocnemididae family (described below), because they are threatened species due to high demand for their eggs and meat.
4. Rafferty, John P (2008). "Side-necked turtle". Britannica. Retrieved November 25, 2021.
5. Gaffney, E. S.; Tong, H.; Meylan, P. A. (2006-11-17). "Evolution of the side-necked turtles: The families Bothremydidae, Euraxemydidae, and Araripemydidae" (PDF). Bulletin of the American Museum of Natural History. 300. New York: American Museum of Natural History: 1–700. doi:10.1206/0003-0090(2006)300[1:EOTSTT]2.0.CO;2. hdl:2246/5824. S2CID 85790134. The relationships of the family Podocnemididae to its sister taxa Hamadachelys and Brasilemys are recognized by placing them in the epifamily Podocnemidinura. The epifamily Podocnemidinura is the sister group to the family Bothremydidae, and together they form the superfamily Podocnemidoidea.
6. Eugene S. Gaffney; Peter A. Meylan; Roger C. Wood; Elwyn Simons; Diogenes De Almeida Campos (2011). "Evolution of the Side-Necked Turtles: The Family Podocnemididae". Bulletin of the American Museum of Natural History. 350: 1–237. doi:10.1206/350.1. hdl:2246/6110. S2CID 83775718. The family Podocnemididae consists of 20 genera and 30 species considered here as valid and diagnosable by cranial characters. Three of these genera and eight species persist into the Recent fauna, barely reflecting the evolutionary diversity and distribution of the group. The family extends from the late Cretaceous to the Recent and occurs in North and South America, Europe, Asia, and Africa.
7. Nardelli, Luciana (February 13, 2020). "Região de Rio Preto identifica tartaruga de 85 milhões de anos" [Rio Preto region identifies 85-million-year-old turtle]. Diário da Região (in Portuguese). Retrieved November 25, 2021. Esse é o perfil da Amabilis uchoensis, a primeira espécie de tartaruga fóssil descrita na região de Rio Preto, descoberta por pesquisadores brasileiros e até da Suíça. O fragmento que permitiu a identificação da nova "tartaruguinha" é um pedaço de crânio que foi localizado em um sítio paleontológico de Ibirá, no ano de 2014. (This is the profile of Amabilis uchoensis, the first fossil turtle species described in the Rio Preto region, discovered by Brazilian and Swiss researchers. The fragment that allowed the identification of the new "little turtle" is a piece of skull that was located in a paleontological site in Ibirá, in 2014.)

External links

• Paleobiology Database Amabilis uchoensis