Acherontemys Temporal range: Lutetian ~ | |
---|---|
Holotype carapace | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Testudines |
Suborder: | Cryptodira |
Superfamily: | Testudinoidea |
Genus: | † Acherontemys Hay, 1899 |
Species: | †A. heckmani |
Binomial name | |
†Acherontemys heckmani Hay, 1899 | |
Acherontemys is an extinct genus of turtle from Eocene sediments in northwestern North America and comprising a single species Acherontemys heckmani. Acherontemys has been placed within the pond turtle superfamily Testudinoidea as part of the clade Pan-Emydidae.
The only known specimen of Acherontemys heckmani was recovered from strata of the Roslyn Formation in Kittitas County, Washington. At the time of description Oliver Perry Hay listed the "Roslyn sandstone" as being of Miocene in age. [1] The formation has subsequently been redated to be of Middle Eocene, Lutetian age, with date constraints between 47.58 ± 0.028 million years ago to 45.91 ± 0.021 million years ago. [2]
The turtle was collected from rocks exposed along a coal seam in the Northern Pacific Railroads Northwestern Improvement Company No. 4 Mine. [1] The mine utilized a vertical shaft with hoist to access coal seams being mined, and had a pump system to prevent water influx filling the workings. [3] The fossil was spotted and recovered by P.Y. Heckman who then passed it on to the Smithsonian for study using paleobotanist Frank Hall Knowlton as an intermediary. Due to the nature of the matrix encasing the fossil, which was described by Oliver Perry Hay as "refractory", only the upper surface of the carapace was excavated, leaving the plastron encased at time of description. Hay's original descriptions of the genus and species were published in an 1899 Proceedings of the United States National Museum paper along with the species description of Hadrianus schucherti , now placed as Cymatholcus schucherti . While no information was given on the derivation of the species name, Hay chose to coin the genus name Acherontemys as a reference to the Acheron river, a "river of the fabled lower world", in combination with the turtle genus Emys . [1]
Hay expressed wishes that additional specimens might be recovered from the mine to give more understanding of the species. [1] However the mine suffered a catastrophic explosion and fire a decade later at 12:45 p.m on October 3, 1909, killing 10 workers and burning down all the mine building except the brick powerhouse. The mine was never reopened. [3]
Acherontemys was originally assigned to the paraphyletic Chelydridae by Hay, a placement maintained by Robert L. Carroll (1988). [4] J. Howard Hutchison (1992), however, classified it within Emydidae, [5] and this placement was maintained by Evangelos Vlachos (2016), who placed it in the Testudinoidea clade Pan-Emydidae. [6] Vlachos notes the extra-wide vertebral scutes as distinguishing A. heckmani from any other testudinoid taxa of North America, though the size is seen in some European geoemydids. [6]
The broad shell of 181 mm (7.1 in) long by 118 mm (4.6 in) wide with a low depressed dome and smooth posterior margin with no serrations. [7] Along the central keel are a series of low bosses. The upper surface is smooth and the sutures are distinct while some areas of the costal shield surfaces are wrinkled. The scutes on the shell were comprised of five notedly large vertebrals, surrounding narrowed costals, and 23 total marginal scutes. Sixteen square marginals are placed, in pairs, at the ends of the four costal scutes, with the remaining marginals along the margins of vertebral scutes I and IV. The costal scutes are narrower than in other genera as a result of the enlarged vertebrals. The vertebrals are extra wide, with Hay (1908) listing vertebral I at 75 mm (3.0 in), vertebral II at 90 mm (3.5 in), vertebral III at 85 mm (3.3 in), vertebral IV at 75 mm (3.0 in) and vertebral V at 65 mm (2.6 in). Vetrabrals II and III are also longer then the other three, which are narrowed to compensate, so much so that the sulcus between III and IV is located over the sixth neural bone rather than the fifth. [7]
Hay interpreted the underlying bones of the shell as having eight neural bones and a single extra large suprapygal. [1] [7] This was later challenged, with Vlachos (2018), after reexamination of the holotype, finding seven pairs of neural bones combined with two suprapygals. He interpreted Hays neural 8 as "suprapygal I" placed directly anterior to "suprapygal II", Hays "pygal" bone, with a narrow front margin, elongated sides, and a rounded rear margin giving a pentagonal outline. [6] Both authors note the distinctly wide nature of superpygal II, which is rectangular in general outline and spans the width of the 3 rear peripheral bones. [7] [6] Along the front margin, damage to the edge of the specimen is noted, with the nuchal bone missing its front edge. [7]
Deposition in the Roslyn Formation paleoenvironment featured westerly flowing rivers and streams [2] and the flora is noted to be lacking in palm trees, which are found in older lowland formations of the area. [8]
The Acheron is a river in the Epirus region of northwest Greece. It is 52 km (32 mi) long, and its drainage area is 705 km2 (272 sq mi). Its source is near the village Zotiko, in the southwestern part of the Ioannina regional unit. The Acheron flows into the Ionian Sea in Ammoudia, near Parga.
The Geoemydidae are one of the largest and most diverse families in the order Testudines (turtles), with about 70 species. The family includes the Eurasian pond and river turtles and Neotropical wood turtles.
Emydidae is a family of testudines (turtles) that includes close to 50 species in 10 genera. Members of this family are commonly called terrapins, pond turtles, or marsh turtles. Several species of Asian box turtles were formerly classified in the family; however, revised taxonomy has separated them to a different family (Geoemydidae). As currently defined, the Emydidae are entirely a Western Hemisphere family, with the exception of two species of pond turtle.
Chelidae is one of three living families of the turtle suborder Pleurodira, and are commonly called Austro-South American side-neck turtles. The family is distributed in Australia, New Guinea, parts of Indonesia, and throughout most of South America. It is a large family of turtles with a significant fossil history dating back to the Cretaceous. The family is entirely Gondwanan in origin, with no members found outside Gondwana, either in the present day or as a fossil.
The Cryptodira are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira in that they lower their necks and pull the heads straight back into the shells, instead of folding their necks sideways along the body under the shells' marginals. They include among their species freshwater turtles, snapping turtles, tortoises, softshell turtles, and sea turtles.
The Cochin forest cane turtle, also known as Kavalai forest turtle, forest cane turtle or simply cane turtle, is a rare turtle from the Western Ghats of India. Described in 1912, its type locality is given as "Near Kavalai in the Cochin State Forests, inhabiting dense forest, at an elevation of about 1500 feet above sea level". Only two specimens were found at that time, and no scientist saw this turtle for the next 70 years. It was rediscovered in 1982, and since then a number of specimens have been found and some studies have been conducted about its phylogeny and ecology.
The Chinese box turtle, also known as the yellow-margined box turtle, or golden-headed turtle, is a species of Asian box turtle. Taxonomically, it is called Cuora flavomarginata.
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.
Acaenasuchus is an extinct genus of pseudosuchian, endemic to what would be presently be known as Arizona during the Late Triassic, specifically during the Carnian and Norian stages of the Triassic. Acaenasuchus had a stratigraphic range of approximately 11.5 million years. Acaenasuchus is further categorized as one of the type fauna that belong to the Adamanian LVF, based on the fauna of the Blue Mesa Member of the Chinle Petrified Forest Formation of Arizona, where Acaenasuchus was initially discovered.
Pachycetus is an extinct genus of pachycetine basilosaurid from Middle Eocene of the eastern United States and Europe. The best known remains generally suggest that Pachycetus lived during the Bartonian, however, fossil finds have also been recovered from sediments of less certain age that could suggest that it may have also lived during the Late Lutetian and Early Priabonian. Pachycetus is primarily known from vertebrae and ribs and is characterized by its highly osteosclerotic and pachyostotic skeleton. This means the bones not only featured thickened rings of cortical bone surrounding the internal cancellous bone, but the cortical bone was furthermore much denser than in other basilosaurids. Two species of Pachycetus are recognized: Pachycetus paulsonii from Europe and Pachycetus wardii from the United States. A third species might be represented by "Zeuglodon" wanklyni.
Phosphatodraco is a genus of azhdarchid pterosaur that lived during the Late Cretaceous of what is now Morocco. In 2000, a pterosaur specimen consisting of five cervical (neck) vertebrae was discovered in the Ouled Abdoun Phosphatic Basin. The specimen was made the holotype of the new genus and species Phosphatodraco mauritanicus in 2003; the genus name means "dragon from the phosphates", and the specific name refers to the region of Mauretania. Phosphatodraco was the first Late Cretaceous pterosaur known from North Africa, and the second pterosaur genus described from Morocco. It is one of the only known azhdarchids preserving a relatively complete neck, and was one of the last known pterosaurs. Additional cervical vertebrae have since been assigned to the genus, and it has been suggested that fossils of the pterosaur Tethydraco represent wing elements of Phosphatodraco.
Pachycheilosuchus is an extinct genus of neosuchian from the Early Cretaceous of Texas, United States. Previously known, in part, as the "Glen Rose form", this crocodylomorph is notable for its procoelous vertebrae, otherwise found only in derived eusuchian crocodilians, a thick margin on the maxillae, and a shield of armor on the neck formed by the fusion of six individual scutes.
Hesperotestudo is an extinct genus of tortoise native to North and Central America from the Early Miocene to the Late Pleistocene. Species of Hesperotestudo varied widely in size, with a large undescribed specimen from the Late Pleistocene of El Salvador reaching 150 cm (4.9 ft) in carapace length, larger than that of extant giant tortoises. Historically considered a subgenus of Geochelone, it is now considered to be distantly related to that genus. Its relationships with other tortoises are uncertain. The exposed areas of the bodies of Hesperotestudo species were extensively covered with large dermal ossicles, which in life were covered in keratin. It has been suggested that species of Hesperotestudo were relatively tolerant of cold weather. Hesperotestudo became extinct at the end of the Pleistocene roughly co-incident with the arrival of the first humans in North America. There is apparently a site in Florida where one individual may have been killed that some suggested were evidence of butchering, although others suggested that the turtle was neither cooked nor does a ledge that was found near it date at the same time as it.
The turtle shell is a shield for the ventral and dorsal parts of turtles, completely enclosing all the vital organs of the turtle and in some cases even the head. It is constructed of modified bony elements such as the ribs, parts of the pelvis and other bones found in most reptiles. The bone of the shell consists of both skeletal and dermal bone, showing that the complete enclosure of the shell likely evolved by including dermal armor into the rib cage.
Eileanchelys is an extinct genus of primitive turtle from the Middle Jurassic (Bathonian) period some 164 million years ago of Britain. Only one species is recorded, Eileanchelys waldmani. It is the best-represented turtle from the Middle Jurassic, because of the amount of specimens that can be assigned to it. The turtle is also one of the oldest turtles ever found to be aquatic, and might represent a milestone in turtle evolution.
Hadrianus is an extinct genus of tortoise belonging to the Testudinidae found in the United States, the Yolomécatl Formation of Mexico, the Alai Beds of Kyrgyzstan and Spain and believed to be the oldest true tortoise known. The genus is thought to be closely related to the genus Manouria. The genus may have evolved in the subtropics of Asia and subsequently migrated to North America and Europe. Evangelos Vlachos (2018) reassessed the North American species attributed to the genus, and determined only two as accepted namely H. corsoni & H. majusculus. The remaining species were identified as either junior synonyms, moved to other genera or considered nomen dubium do to incomplete fossils.
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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.
Polystoechotites is an extinct parataxon of lacewings in the moth lacewing family Ithonidae. The taxon is a collective group for fossil polystechotid giant lacewing species whose genus affiliation is uncertain, but which are distinct enough to identify as segregate species. Polystoechotites species are known from Eocene fossils found in North America and is composed of four named species Polystoechotites barksdalae, Polystoechotites falcatus, Polystoechotites lewisi, and Polystoechotites piperatus, plus two unnamed species. Three of the described species are known from fossils recovered from the Eocene Okanagan Highlands of Washington State, while the fourth is from Colorado.