[D] Ceratonykus oculatus ~/~
Describer
Alifanov & Barsbold 2009
Time
Cretaceous Late Santonian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Alvarezsauridae
Diet
Carnivore
Fossilsite
Barun Goyot Formation. South Gobi Aimag, Nemegt Depression, Khermiin Tsav locality, Mongolia
Info
Ceratonykus oculatus gen. et sp. nov. (Parvicursoridae, Alvarezsauria), from the Upper Cretaceous (Baruungoyot Formation) of Mongolia is described based on a fragmentary skeleton. It differs from other alvarezsaurians in many characters, including the short femora, long tarsometatarsals, and considerably reduced third metatarsals. The carpometacarpals contain spikelike bones. The natural endocast of the new taxon shows large acoustic tubercles, the ventral position of the optic lobes in the midbrain, and the absence of a vertical flexure at the brain floor. The data obtained cast doubt on the taxonomic position of alvarezsaurians in the Theropoda.
Holotype
MPC, no. 100/124, incomplete skull including incomplete lower jaw, postcranial elements (several cervical and caudal vertebrae, sternum, right and left coracoids, a right humeral fragment, distal elements of forelimbs, fragmentary ilium, and hind limbs);
Etymology
From the Greek ceratinus (horned) and onyx (claw) – From the Latin oculatus (sharpsighted, big-eyed).
Diagnosis
Preorbital skull region long. Upper temporal fenestrae ovate, 0.4 as long as frontals. Length of one frontal almost four times greater than its width. Frontals narrowing rostrally in narrow wedge. Prefrontals adjoining each other medially. Basipterygoid processes two-thirds as high as quadrates. Labiooccipitally, dentaries forming deep and rostrally tapering depression. Mandibular fenestrae extensive. Centra of cervical and anterior caudal vertebrae narrow. Deltopectoral crest separated from humeral head by notch. Basal phalanx of major digit of manus extended, its flanks moderately wide, and distal condyle narrow, symmetrical. Postacetabular plate of ilia with relatively small longitudinal craniomedial crest. Femora strongly curved, nearly half as long as tibiotarsus. Fourth trochanter distinct.
Cnemial crest of tibiae undeveloped. Ascending process of astragali high and wide. Tarsometatarsals 1.33 as long as femora. Second and fourth metatarsals tightly adjoining each over entire extent; their dorsal and palmar surfaces ridgelike, deep grooves formed between these bones. Deep notch formed proximodorsally between these metatarsals. Distally, second metatarsals shorter than fourth. Tarsometatarsals 3.5 times as long as third metatarsals. Basal phalanx of fourth digit of hind feet only slightly shorter than basal phalanx of second digit.
Alifanov & Barsbold 2009
Time
Cretaceous Late Santonian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Alvarezsauridae
Diet
Carnivore
Fossilsite
Barun Goyot Formation. South Gobi Aimag, Nemegt Depression, Khermiin Tsav locality, Mongolia
Info
Ceratonykus oculatus gen. et sp. nov. (Parvicursoridae, Alvarezsauria), from the Upper Cretaceous (Baruungoyot Formation) of Mongolia is described based on a fragmentary skeleton. It differs from other alvarezsaurians in many characters, including the short femora, long tarsometatarsals, and considerably reduced third metatarsals. The carpometacarpals contain spikelike bones. The natural endocast of the new taxon shows large acoustic tubercles, the ventral position of the optic lobes in the midbrain, and the absence of a vertical flexure at the brain floor. The data obtained cast doubt on the taxonomic position of alvarezsaurians in the Theropoda.
Holotype
MPC, no. 100/124, incomplete skull including incomplete lower jaw, postcranial elements (several cervical and caudal vertebrae, sternum, right and left coracoids, a right humeral fragment, distal elements of forelimbs, fragmentary ilium, and hind limbs);
Etymology
From the Greek ceratinus (horned) and onyx (claw) – From the Latin oculatus (sharpsighted, big-eyed).
Diagnosis
Preorbital skull region long. Upper temporal fenestrae ovate, 0.4 as long as frontals. Length of one frontal almost four times greater than its width. Frontals narrowing rostrally in narrow wedge. Prefrontals adjoining each other medially. Basipterygoid processes two-thirds as high as quadrates. Labiooccipitally, dentaries forming deep and rostrally tapering depression. Mandibular fenestrae extensive. Centra of cervical and anterior caudal vertebrae narrow. Deltopectoral crest separated from humeral head by notch. Basal phalanx of major digit of manus extended, its flanks moderately wide, and distal condyle narrow, symmetrical. Postacetabular plate of ilia with relatively small longitudinal craniomedial crest. Femora strongly curved, nearly half as long as tibiotarsus. Fourth trochanter distinct.
Cnemial crest of tibiae undeveloped. Ascending process of astragali high and wide. Tarsometatarsals 1.33 as long as femora. Second and fourth metatarsals tightly adjoining each over entire extent; their dorsal and palmar surfaces ridgelike, deep grooves formed between these bones. Deep notch formed proximodorsally between these metatarsals. Distally, second metatarsals shorter than fourth. Tarsometatarsals 3.5 times as long as third metatarsals. Basal phalanx of fourth digit of hind feet only slightly shorter than basal phalanx of second digit.