Salinites grossicostatum (Imlay, 1939) and S. finicostatum sp. nov. from the latest Tithonian (Late Jurassic) of northeastern Mexico

Abstract

Based on our taxonomic revision of the ammonite Salinites grossicostatum from the uppermost Tithonian of the La Caja Formation at Puerto Piñones, in the state of Coahuila, northeastern Mexico, we suggest that some specimens described from other Tithonian sites of Cuba and Mexico assigned to S. grossicostatum belong to a new species, here presented as S. finicostatum. Salinites grossicostatum and S. finicostatum sp. nov. are endemic to the ancient Gulf of Mexico and are restricted to outer continental shelf environments.

First Record of Sexual Dimorphism in Toxasterid Echinoid Heteraster from the Early Cretaceous Deposits of the Kopet‐Dagh Basin, NE Iran

“…SSD is common in many invertebrates and is probably best interpreted as the result of sexual selection (Hedrick and Temeles, 1989;Anderson, 1994;Cox et al, 2003;Silina, 2016). In most invertebrates, female individuals are larger than male ones, for example, in some Mesozoic ostracodes the females have a larger carapace (Ozawa, 2013), also in bivalves (Silina, 2016), starfishes (Ohshima and Ikeda, 1934), ammonites (Parent and Zatoń, 2016;Zell and Stinnesbeck, 2016), gastropods (Morse, 1876;Má rquez and Averbuj, 2016;Ng et al, 2019) and echinoids (Hamel and Himmelman, 1992;Abessa et al, 2001;Jeffery et al, 2003). However, this is not always the case, and in some invertebrates the males are larger than the females, as in some Cenozoic podocopid ostracodes (Ozawa, 2013) and scleractinian Plastron type is semiamphisternous, Labrum (Lb) is triangular and attached anteriorly to the peristome (Pr) and followed by two asymmetrical sternal plates (St).…”