Alpkarakush kyrgyzicus Rauhut, Bakirov, Wings, Fernandes & Hübner, 2024, sp. nov.

Alpkarakush kyrgyzicus sp. nov. ZooBank LSID: urn:lsid:zoobank.org:act: 2ABC5B5C-7119- 4D12-842F-1CB9D88CF2CB. Etymology: The species epithet refers to the Kyrgyz Republic, the provenance of the type specimen. Holotype: Partial skeleton (Fig. 3), including both postorbitals (IGB 2-1, 2-2), the left quadratojugal (IGB 2-9), two posterior dorsal vertebral centra (IGB 2-10,2-11), two partial dorsal neural spines (IGB 2-12, 2-13) and a fragment of the dorsal neural arch (IGB 2-22), five sacral vertebrae (IGB 2-14, 2-15), several dorsal ribs (IGB 2-16, 2-17, 2-18, 2-19, 2-20, 2-21), a manual phalanx (IGB 2-24), a manual ungual (IGB 2-47), a partial left ilium (IGB 2-25), a partial pubes (IGB 2-26, 2-27, 2-28, 2-29), both articulated ischia (IGB 2-30, 2-31), a complete left (IGB 2-32) and right (IGB 2-33) femora, a complete left (IGB 2-34) and right tibiae (IGB 2-35), an almost complete left fibula (IGB 2-36, 2-37), left and right astragalocalcanea (IGB 2-38, 2-39), a partial left distal tarsal IV (IGB 2-40), a left metatarsal II (IGB 2-41), a left and right metatarsal III (IGB 2-42, 2-43), a pedal phalanx (IGB 2-44), and two pedal unguals (IGB 2-45, 2-46). Paratype: Fragmentary postcranium of a smaller individual, from the same locality as the holotype, including the left and right pubes (IGB 2-49, 2-50, 2-51, 2-52), a proximal fragment of the right ischium (IGB 2-53), and a right tibia (IGB 2-48). Referred material: Several isolated teeth (IGB 2-3, 2-4, 2-5, 2-6, 2-7, 2-8, 2-27) and a furcula (IGB 2-23) from the type locality are referred to the same taxon. In the case of the teeth IGB 2-6, 2-7, 2-8, and 2-27, this referral should be regarded as tentative (see below). 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. 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. Description Cranium Only both postorbitals and the left quadratojugal are preserved of the cranium. In addition, several teeth were collected from the site, at least several of which represent the same taxon with high certainty. Postorbital: Both postorbitals are preserved (Fig. 4). The left element (IGB 2-1) is complete (Fig. 4A–D), while the right postorbital (IGB 2-2) has been reconstructed from numerous fragments and misses several of the finer margins (Fig. 4E, F). As in most non-maniraptoriform theropods, the postorbital is a triradiate, T-shaped bone, in which the ventral (jugal) process is considerably longer than either the anterior (frontal) or posterior (squamosal) processes. The postorbital is c. 20 cm high and 17.5 cm long over the anterior and posterior processes, of which the anterior process is longer (c. 8 cm) than the posterior process (5 cm). The most conspicuous character of the postorbital is an extremely developed, rugose orbital brow that covers the posterior two-thirds of the anterior process and the anterior half of the junction of the three processes (Fig. 4A, D, E). This brow forms a massive lateral and dorsal swelling with a rugose lateral surface, composed of numerous small tubercles, giving it a granulate texture. It considerably overhangs the posterodorsal part of the orbital cavity, thus forming a mediolaterally deeply concave dorsomedial surface of this opening at the junction of the processes.Strongly developed postorbital brows are generally present in carcharodontosaurids (e.g. Sereno et al. 1996, Coria and Currie 2006, Canale et al. 2022), and also in the metriacanthosaurids (Dong et al. 1983, Currie and Zhao 1993, Gao 1999). However, whereas carcharodontosaurids usually have an ornamentation of ridges and grooves, metriacanthosaurids show a similar granulated structure as it is also present in Alpkarakush. From the posterior margin of the brow, a marked oblique step extends posteroventrally over the lateral surface of the ventral process (Fig. 4A), as in Sinraptor (Currie and Zhao 1993). This step meets the convex posterior margin of this process at approximately its half height and separates a smooth posterodorsal surface from a more rugose anteroventral surface, which covers most of the lateral surface of the ventral process, similar to the condition in many abelisaurids (e.g. Sampson and Witmer 2007, Cerroni et al. 2020). Similar low rugosities also cover the lateral and dorsal surfaces of the anterior process anterior to the orbital brow. The anterior end of the anterior process is turned ventrally, as in Irritator (Schade et al. 2023). The anterior margin of the anterior process is massive (c. 15 mm thick dorsoventrally), but lacks an articular facet for the lacrimal/prefrontal, indicating that the latter elements did not contact the postorbital, in contrast to abelisaurids (Bonaparte and Novas 1985, Bonaparte et al. 1990, Sampson and Witmer 2007) and carcharodontosaurids (Sereno et al. 1996, Coria and Currie 2002, Sereno and Brusatte 2008). The posterior process is short and spike like, being wider mediolaterally than dorsoventrally over its entire length, as in Sinraptor (Currie and Zhao 1993), but in contrast to most theropods, where this process usually forms a dorsoventrally oriented, triangular sheet of bone (e.g. Madsen 1976, Britt 1991, Brusatte et al. 2012, Rauhut et al. 2016). In dorsal view, this process tapers posteriorly and shows weak longitudinal striations where it was overlapped by the squamosal (Fig. 4D). There is a marked asymmetry in the development of the lateral surface of the posterior process of the left and right postorbital; whereas it is dorsoventrally narrow in the former, and was probably underlain by the ventral anterior process of the squamosal, the right element shows a deep longitudinal groove on the lateral surface of this process (Fig. 4E), in which the anterior process of the squamosal might have fitted. A similar groove on the lateral side of the posterior process of the postorbital is found in Sinraptor (Currie and Zhao 1993). In medial view, a marked ridge forms the posterior and posterodorsal margins of the orbit and extends from the anteromedial end of the anterior process to the ventral end of the ventral process (Fig. 4C, F). A stout flange of bone extends from the ventral end of this ridge towards the base of the posterior process, thus forming the markedly convex dorsal part of the anterior margin of the infratemporal fenestra; the ventral part of this margin was formed by the dorsal process of the jugal, which the postorbital overlapped anteriorly in the ventral third of its height. The facet for the jugal is developed as a broad, posteriorly opening groove on the posterior surface of the orbital ridge (Fig. 4B), as in megalosauroids (e.g. Britt 1991, Sereno et al. 1994, Sadleir et al. 2008, Rauhut et al. 2016, Schade et al. 2023). Anterior to the orbital ridge, a small anterior flange intruding into the orbit was obviously present, similar to the situation in Sinraptor (Currie and Zhao 1993) and other metriacanthosaurids (Gao 1999), but is damaged on both sides. At the junction of the three processes, a deep, oval depression dorsal to the orbital ridge marks the contact with the laterosphenoid. (Fig. 4C, F) In dorsal view, the supratemporal fossa extends onto the medial side of the anterior process of the postorbital and forms a smooth, dorsally facing shelf anterior to the laterosphenoid articulation (Fig. 4D), as in Sinraptor (Currie and Zhao 1993). Anteromedial to this shelf, the relatively thin articular surface for the frontal is marked by a groove in the anteromedial margin of the bone. Behind the laterosphenoid articulation, the margin of the supratemporal fossa extends onto the dorsal surface of the medial side of the junction of the three processes and is offset posteroventrally by a marked step from the medial surface of the posterior flange on the ventral process. Posterodorsally, an abrupt flexure separates the margin of the supratemporal fossa from the dorsal surface of the base of the posterior process. This surface is flat and marked by a sharp dorsal rim laterally. Apparently, all of this surface was overlapped by the dorsal process of the squamosal, as indicated by the sharp lateral rim and a small raised lip at the anterior end of this surface (Fig. 4D). If this really was the case, the dorsal anterior process of the squamosal would have reached considerably more anteriorly than the ventral process and would have reached the level of the poste