User:HouseOfChange/Algorachelus

Algorachelus is an extinct genus of turtles belonging to the family Bothremydidae. When first described in 2017, it represented "the oldest known dispersal event of the crown Pleurodira from Gondwana to Laurasia."

The genus is named for the Spanish town Algora, where the type species A. peregrinus was first discovered.

Algorachalus and the dispersal of pleurodiran turtles
Pan-Pleurodira, the crown group of modern "side-necked" turtles, first appeared in Gondwana in the early (or lower) Cretaceous, during the Barremian age (that is, between roughly 130 Ma (million years ago) and 125 Ma.) Nearly all surviving pleurodires live in warm-weather regions of Africa and South America that were once part of Gondwana. Because pleurodires have their pelvis fused to the shell, they are awkward on land, and all surviving species are aquatic.

Roughly 50 Ma, Gondwana collided with the northern supercontinent Laurasia. Several species of bothremydid turtles, however, had adapted to "near-shore marine conditions" and were thus able to migrate from Africa to Europe while the Tethys Sea gap was still large. For example, the bothremid Rosasia soutoi was already in Portugal during the late Campanian-early Maastrichtian (c. 70–80 Ma.) Describing the bothremid Foxemys (France and Hungary, Santonian c. 85 Ma), Rabi et al. (2012) state "the migration could only happen after the Bothremydina physiologically adapted to a marine habitat and their osmoregulatory systems were developed enough to constantly live in saltwater."

According to its discoverer Adán Pérez-García, the species Algorachelus peregrinus originated in Northern Africa "during the Upper Cretaceous" but migrated from its coastal environment there to Europe about 95 million years ago, well before the closure of the Tethys Sea.

Joyce et al attribute the following to Gaffney2006 "bothremydids are notable for exhibiting high levels of cranial disparity indicative of generalist, molluscivorous, and piscivorous diets and for inhabiting freshwater, estuarine, and costal environments (Gaffney, Tong & Meylan, 2006)."

They also say the following: "The family Bothremydidae is a large and diverse group extending from the Albian to the Eocene in North and South America, Europe, Africa, and India. Its monophyly is supported by the presence of a wide exoccipital-quadrate contact, a eustachian tube separated from the incisura columellae auris usually by bone to form a bony canal for the stapes, absence of a fossa precolumellaris, a supraoccipital-quadrate contact (except in the tribe Taphrosphyini), and a posterior enlargement of the fossa orbitalis. Although there is a diversity of triturating surfaces within the family, primitively bothremydids have a posteriorly wide triturating surface with a significant palatine contribution in the upper jaw."

Type species Algorachelus peregrinus

 * Algorachelus peregrinus Pérez-García 2017 Utrillas Formation, Spain, Nazaré, Portugal, Late Cretaceous (Cenomanian)

The genus name combines "Algora," the name of the town where first type specimen was found, with "chelus," a Latinization of the Greek word for "tortoise." The species name "peregrinus" means "wandering."

Despite Algora's location in central Spain, it seems to have been coastal in the Cenomanian, with sandy sediments and evidence of tides. The Utrillas Formation also shows evidence of erosion by rivers.

Turtle shells that Pérez-García assigned to A. peregrinus were later discovered in Cenomanian sites in Nazaré (Portugal, 2017) and in Cabrejas del Pinar (Spain, 2020).

Other species
Two other species of extinct turtles, previously described by other researchers, have also been assigned to Algorchalus by Pérez-García.
 * Algorachelus parva (Haas 1978) Bet-Meir Formation, Amminadav Formation, Palestine, Late Cretaceous (Cenomanian,) also described as Podocnemis judaea and Podocnemis parva.
 * Algorachelus tibert (Joyce et al. 2016) Naturita Formation, Utah, Late Cretaceous (Cenomanian) The assignment of this species to Algorachelus is disputed by some who consider it instead the only species of the genus Paiutemys.