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| Alpkarakush kyrgyzicus Rauhut, Bakirov, Wings, Fernandes & Hübner, 2024 |
Abstract
Recent fieldwork in the late Middle Jurassic Balabansai Formation of Kyrgyzstan has yielded a partial skeleton of a large theropod dinosaur. The material includes a few bones of the skull (postorbital, quadratojugal), dorsal and sacral vertebrae, fragments of the pectoral girdle and forelimbs, and an almost complete pelvic girdle and hindlimbs, and is here made the type of a new theropod taxon, Alpkarakush kyrgyzicus gen. et sp. nov. Alpkarakush can be diagnosed by an extremely developed orbital brow on the postorbital, a pneumatic opening leading into cavities in the neural arch from the centroprezygodiapophyseal fossa in the posterior dorsal vertebrae, an almost enclosed ventral sulcus in manual phalanx II-1, a narrow and deep intercondylar groove on the anterior side of the distal femur, and an epicondylar crest on the distal femur that is offset from the distal end. A second, fragmentary, and smaller specimen from the same site represents the same taxon. Based on long bone histology, the type of Alpkarakush represents a late subadult individual, whereas the smaller specimen is a juvenile, possibly indicating gregarious behaviour. Phylogenetic analysis places Alpkarakush in the Metriacanthosauridae, underlining the diversity and wide distribution of this clade in the Jurassic of Asia.
Central Asia, Middle Jurassic, Tetanurae, Metriacanthosauridae, bone histology
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| Outline reconstruction of Alpkarakush kyrgyzicus, with recovered elements indicated. Scale bar is 1 m. |
SYSTEMATIC PALAEONTOLOGY
Dinosauria Owen, 1842,
Saurischia Seeley, 1887,
Theropoda Marsh, 1881,
Tetanurae Gauthier, 1986,
Metriacanthosauridae Paul, 1988
Alpkarakush gen. nov.
Etymology: Named after Alpkarakush, a mythological large bird [Алпкаракуш] that often comes to the help of heroes in critical moments in the ‘Manas’ epos, one of the central mythological elements in Kyrgyz culture (Seiilbek et al. 2018).
Alpkarakush kyrgyzicus sp. nov.
Etymology: The species epithet refers to the Kyrgyz Republic, the provenance of the type specimen.
Diagnosis: Alpkarakush kyrgyzicus can be diagnosed by the following combination of characters (autapomorphies are indicated by *): extremely developed supraorbital brow on the postorbital, overhanging the orbit; posterior dorsal vertebrae with a channel leading from the centroprezygodiapophyseal fossa posteromedially into pneumatic chambers in the neural arch*; sacral vertebrae with fused neural spines that are approximately as high as the combined height of the vertebral centrum plus neural arch; manual phalanx II-1 with a ventral sulcus proximally that is almost completely enclosed by medial and lateral ventral flanges*; dorsal margin of the ilium slopes steeply posteroventrally*; brevis fossa on ilium reduced to a small medial shelf; shaft of pubis strongly bowed anteriorly; well-developed longitudinal depression on the posterolateral side of the pubic shaft adjacent to the pubic boot (based on paratype); unusually high pubis/tibia ratio (1.22 or higher); articulated ischia with pronounced ischial boots that are convex distally and fused anteriorly, but separated posteriorly; ischium with small obturator flange that is offset from the pubic peduncle; pubic peduncle of ischium very long; iliac articulation in proximal ischium cup-shaped; narrow and deep intercondylar groove on the anterior side of distal femur*; robust and well-developed medial epicondylar crest on distal femur, considerably offset proximally from distal end*; tibia with robust, bulbous fibular flange; astragalus and calcaneum fused.
Type locality and horizon: Locality FTU-1, just west of the town of Tashkumyr, Jalal-Abad Oblast, Kyrgyzstan (Figs 1, 2). The specimens were found in the higher part of the Balabansai Formation, Callovian.
Oliver W. M. Rauhut, Aizek A. Bakirov, Oliver Wings, Alexandra E. Fernandes and Tom R. Hübner. 2024. A new theropod dinosaur from the Callovian Balabansai Formation of Kyrgyzstan. Zoological Journal of the Linnean Society. 201(4); zlae090. DOI: doi.org/10.1093/zoolinnean/zlae090
