The terebratulid Kutchithyris (Brachiopoda) from the Jurassic sequence of Kutch, western India-revisited

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The Kutch basin developed due to the fragmentation of Gondwana during the Middle Jurassic and hosted diverse endemic fauna, of which brachiopods are one of the chief constituents. The dominant brachiopod faunal element is the terebratulid genus Kutchithyris Buckman. The genus is represented throughout the exposed Middle Bathonian to Oxfordian sequence in Kutch and is also reported sporadically from outside Kutch. The systematics of this small but distinct clade is in a state of flux. The present paper focuses on revising the systematics of the genus and its three dominant species, namely, K. acutiplicata, K. propinqua and K. euryptycha, based on numerous specimens collected from the field with precise stratigraphical and sedimentological background and the type materials. They constitute an evolving lineage, and have been known from the Upper Bathonian rocks of the Pamirs, where they are cited as one of the celebrated examples of rapid speciation. A detailed comparison of the specimens from these two areas reveals that the speciation took place in Kutch and involved cladogenesis. Thus, it provides a good example of the punctuational model of evolution.
日本古生物学会の論文