Kyhytysuka (Chibcha pronunciation: [kɨhɨtɨˈsuka]) 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.
Discovery and naming The first definitive ichthyosaur remains in Colombia were discovered in the 1970s in the Paja Formation of Villa de Leyva. This fossil, a three-dimensionally preserved skull discovered by local Jorge Cárdenas, was described as a new species of Platypterygius, P. sachicarum, by María Páramo-Fonseca in 1997. However the taxon went largely ignored in the following years or was unofficially considered to be synonymous with the Argentinian Platypterygius hauthali. Further research on ichthyosaurs since its discovery have rendered the original description inadequate and furthermore found the genus of Platypterygius as taxonomically problematic. Further discoveries were made including postcranial material assigned to P. sachicarum and partial forelimbs considered to be Platypterygius sp. In 2021 Cortés et al. published a redescription of the holotype skull, finding it to represent a distinct genus they named Kyhytysuka sachicarum. The holotype, specimen DON-19671, is currently held at the Museo Geológico Nacional José Royo y Gómez, Colombian Geological Survey. The name Kyhytysuka derives from two words of the indigenous Muisca language. The name is composed of the verb "kyhyty" and the particle "suka", in combination meaning "the one that cuts with something sharp" in reference to the animal's unique dentition. The specific name "sachicarum" was coined in 1977 and was originally conceived to refer to a "Sáchicas" indigenous community. Instead it refers to the town of Sáchica, despite the fact that the holotype was discovered in Villa de Leyva.
Description Kyhytysuka was a medium-sized ichthyosaur, with the largest specimen CIP-GA-01042014 measuring around 5 metres (16 ft) in length. Its entire skull measures 940 mm in length from the tip of the premaxilla to the posterior end of the mandible. The premaxilla is relatively robust when compared to other ophthalmosaurs and slightly convex in shape. The premaxilla makes up most of the rostrum and houses a shallow alveolar groove that's deepest at the premaxillary-maxillary contact and grows wider and shallower towards the tip of the snout. The contact to the maxilla is poorly preserved; however, the contact to the nasal is clearly visible as it overlaps the premaxilla posterodorsally. The maxilla measures 320 mm in length and contacts the lacrimal and jugal, but not the prefrontals. The maxilla has delicate striations on its dorsolateral surface and a smooth groove on the last 2/3 of the lateral surface. The subcircular external nares are surrounded by the maxilla, lacrimal and over most of its dorsal surface the nasal. The nasal is 50 cm long and makes up 2/3 of the rostrum's dorsal surface. The areas closest to the tip of the snout are dorsally slightly convex and become more squared towards the posterior of the bone. The lacrimal is longer than high with a broad contact to the maxilla. The bone has three projections, a subnarial, suborbital and an ascending process, the later two of which crescent shaped. The jugal is dorsoventrally compressed with ridges at the end of the maxilla suggesting that the two bones made broad contact. The bone forms the ventral margin of the orbits and connects to the postorbital bone behind the eyes. The frontal is narrow and saddle shaped behind the orbits and widens towards its contact with the prefrontals before growing narrower again as it drives a wedge between the nasal bones. The parietal makes up the bulk of the dorsal skull roof, is broad and dorsoventrally thick and weakly convex. The orbits were large and oval, however the external sclerotic ring is not preserved. There are however several disarticulated sclerotic fragments present in the fossil. The dentary is the longest bone in the fossil, measuring a total of 720 mm, and makes up the majority of the mandible. It contains a long tooth groove with space for 47 dentary teeth that ends approximately at the anterior boundary of the narial fossa. The mandibular symphysis makes up 40% of the mandible, with 2/3 of it being made up by the extensive splenial bone. In lateral view the surangular contributes more to the surface of the mandible than the angular. The left lower jaw of the Kyhytysuka holotype may even preserve connective tissue similar to a Stenopterygius quadriscissus specimen from Holzmaden. However these elements are not well preserved and may also represent teleost fish bones or plant remains with carbonate replacement.
… excerpt ends here. Continue reading the full article.
