First population-level study of the ammonite genus Hildoglochiceras Spath, and the Lower Tithonian record of the Hildoglochiceras Horizon in the Kachchh Basin, India Author Pandey, Dhirendra Kumar Department of Geology, School of Earth, Biological and Environmental Science, Central University of South Bihar SH 7, Gaya-Panchanpur Road, Village Karhara, Post Fatehpur, Gaya 824236 (Bihar), India dhirendrap@cusb.ac.in Author Fuersich, Franz T. FG Palaeoumwelt, GeoZentrum Nordbayern der Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Loewenichstrasse 28, 91054 Erlangen, Germany Author Alberti, Matthias State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Centre for Research and Education on Biological Evolution and Environment and Frontiers Science Center for Critical Earth Material Cycling, Nanjing University, Nanjing 210023, Jiangsu Province, China Author Das, Ranajit https://orcid.org/0000-0001-5308-3477 Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore- 575018, India Author Saez, Federico Oloriz Departamento de Estratigrafia y Paleontologia, Fac. Ciencias, Univ. Granada, Severo Ochoa s / n, Spain text Zitteliana 2022 2022-03-02 96 1 49 http://dx.doi.org/10.3897/zitteliana.96.73892 journal article http://dx.doi.org/10.3897/zitteliana.96.73892 2747-8106-96-1 D5F97D7240455065AD6C43481AAD2D6D Aulacosphinctoides sp. ind. Fig. 11G-I Material. One specimen, Hildoglochiceras Bed of Jara Dome (Lower Tithonian); KSKV2020Jara/13. Description. Shell moderately large (ca. 55 mm in diameter), evolute and depressed. Whorl section subcircular with uniformly arched flanks, umbilical shoulder regions and broad venter. Ornamentation consists of prorsiradiate, biplicate ribs, branching above mid-lateral height into finer secondary ribs, crossing ventral region almost straight. Primary ribs thick, moderately spaced, originating from umbilical suture slightly rursiradially. Occasionally, single primary rib. Constrictions seen on inner whorls. Umbilical wall steeply inclined. Remarks. The outer whorl represents the body chamber, filled with micrite with dispersed coarse quartz grains. There is no sign of any suture lines. The specimen is slightly deformed showing an almost flat right lateral surface with maximum inflation at the ventro-lateral shoulder, whereas the left lateral surface is uniformly arched with the region of maximum inflation at mid-lateral height. The depressed whorl section, biplicate thick ornamentation and presence of constrictions in the inner whorls suggest the genus Aulacosphinctoides Spath. Due to the fragmented and deformed nature of the specimen a species identification is not possible. Nevertheless, the morphological characters are comparable with Aulacostephanoides infundibulus ( Uhlig 1910 : 371, pl. 66, fig. 3a-c, pl. 72, figs la-c (= lectotype), 2a-c, 3a, b, 4a-c; Yin and Enay 2004 : pl. 3, fig. 7a, b; Enay 2009 : 181, pl. 42, fig. la-c). Biostratigraphy. The Aulacosphinctoides or Virgatosphinctes and Aulacosphinctoides assemblage suggests an earliest Tithonian age (see above) ( Uhlig 1903 , 1910 ; Spath 1933 : 673; Pathak 1997 , 2007 ; Pandey and Krishna 2002 ; Yin and Enay 2004 ; Enay 2009 ; Pandey et al. 2010 , 2013 ).