''Ocepechelon'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of giant protostegid

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...

known from

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

(late

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from ...

stage, 67 Myr) phosphatic deposits of the Oulad Abdoun Basin,

Khouribga Province Khouribga (in خريبكة ) is a province of Morocco in the region of Béni Mellal-Khénifra. It has a population of 499,144 people, with a majority from Arab root The major cities and towns are# Bejaad # Boujniba # Boulanouare # Hattane # Khouri ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria to ...

. It is known from the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

OCP DEK/GE 516, a complete but isolated 70-cm-long

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

, making it one of the largest marine turtles ever described. It was first named by Nathalie Bardet, Nour-Eddine Jalil, France de Lapparent de Broin, Damien Germain, Olivier Lambert and Mbarek Amaghzaz in

2013 File:2013 Events Collage V2.png, From left, clockwise: Edward Snowden becomes internationally famous for leaking classified NSA wiretapping information; Typhoon Haiyan kills over 6,000 in the Philippines and Southeast Asia; The Dhaka garment fact ...

and the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

is ''Ocepechelon bouyai''. The feeding apparatus of ''Ocepechelon'', a bony

pipette A pipette (sometimes spelled as pipett) is a laboratory tool commonly used in chemistry, biology and medicine to transport a measured volume of liquid, often as a media dispenser. Pipettes come in several designs for various purposes with diffe ...

-like snout, is unique among

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...

s and shares unique convergences with both

syngnathid The Syngnathidae is a family of fish which includes seahorses, pipefishes, and seadragons (''Phycodurus'' and ''Phyllopteryx''). The name is derived from grc, σύν (), meaning "together", and (), meaning "jaw". The fused jaw is one of the tra ...

fishes (unique long tubular bony snout ending in a rounded and forward directed mouth) and

beaked whale Beaked whales (systematic name Ziphiidae) are a family of cetaceans noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well-k ...

s (large size and elongated

edentulous Toothlessness, or edentulism, is the condition of having no teeth. In organisms that naturally have teeth, it is the result of tooth loss. Organisms that never possessed teeth can also be described as edentulous. Examples are the members of the ...

jaws).

Description

''Ocepechelon'' is known solely from an isolated yet complete skull, 70 cm in length. From the size of the skull, it must have been one of the largest turtles that ever lived. The skull of this genus was not only exceptional in size, but also in appearance: large at the back, it narrowed at the front to form a sort of elongated, narrow, bony funnel. The lower jaw and hyoid remain unknown, but from the skull itself, which is 70 cm in length, a wide range of information can be determined. The skull roof of ''Ocepechelon'' is

dorsoventrally Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

compressed, with a wide cerebral cavity and a lateral wall of the '' cavum cranii'' that is anteromedially bowed. Its longirostrine snout has been compared to a

, and is unique among all tetrapods. Its flattened, streamlined skull, as well as the dorsal position of its orbits and nares, suggest it was a seagoing species which hunted close to the water's surface. This hypothesis is supported by sedimentological analysis and its skull anatomy. Several aspects of ''Ocepechelons skull anatomy suggest it may have been a suction feeder, namely the tube-like upper jaw. In general, the skull must have looked something like a toothless crocodile: there were no teeth, but the eyes were upturned, as were the nostrils, which were set far back. It is the only tetrapod to have developed an evolutionary convergence with both syngnathid fishes and beaked whales, since it possessed a large head but a long, narrow, toothless snout. Like other genera in the Panchelonioidea, it likely possessed limbs that had evolved into flippers, allowing an active swimming lifestyle. Material which may be preferable to ''Ocepechelon'' supports this hypothesis.

Phylogeny

Due to the limited fossil material available, numerous methods were used to assess the phylogenetic position of the animal. The removal of outgroup taxa, except for the hypothetical taxon, deliberated some relationships and showed that ''Ocepechelon'' and ''Bouliachelys'' could be basal dermochelyoids, forming a polytomy with the Dermochelyidae and Protostegidae. The inclusion of Chelomacryptodira resolved this polytomy, and suggested that ''Ocepechelon'' was the most basal dermochelyid known. Below is a cladogram from the description of ''Ocepechelon'', by Bardet et al., (2013). However, Scavezzoni & Fischer (2018), who both recovered it as a protostegid.

Paleobiology

The remarkable similarities between ''Ocepechelon'' and

beaked whales Beaked whales (systematic name Ziphiidae) are a family of cetaceans noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well-kn ...

(as well as

fishes) have led paleontologists to speculate about ''Ocepechelon'''s possible mode of feeding. Since both beaked whales and syngnathids are organisms that feed by sucking (i.e., creating a vacuum to suck in small prey), paleontologists believe that ''Ocepechelon'' may have also fed in this way. This animal probably swam near the surface of the warm oceans it inhabited, swallowing large quantities of small fish, cephalopods and jellyfish. From comparison with other present-day turtles, it is also speculated that ''Ocepechelon'' may have been equipped with small spiny structures within its throat. These papillae are currently present in the

leatherback sea turtle The leatherback sea turtle (''Dermochelys coriacea''), sometimes called the lute turtle or leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to and weights ...

(one of ''Ocepechelon'''s closest relatives), and not only filter water, but also create a sharp barrier to prey trying to get out. ''Ocepechelon'' may have had a similar structure, as well as other papillae along the edges of the mouth.

References

{{Testudines Protostegidae Prehistoric turtle genera Late Cretaceous turtles Maastrichtian life Late Cretaceous reptiles of Africa Fossils of Morocco Fossil taxa described in 2013 Articles containing video clips Extinct turtles