A new species of the clypeasteroid echinoid Astrodapsis from the Miocene Isidro Formation, Baja California Sur, Mexico

Abstract

The clypeasteroid echinoid Astrodapsis bajasurensis n. sp. is described from upper middle Miocene beds of the Isidro Formation near the mouth of Arroyo Mezquital on the Pacific coast of north-central Baja California Sur, Mexico. The new species is the first occurrence of Astrodapsis outside of California and extends the southern limit of the genus by 1,100 km.

Vaquerosella perrillatae sp. nov.: A Miocene species of Echinarachniidae (Echinodermata: Clypeasteroida) from Baja California Sur, Mexico

“…The specimens here reported have an oral periproct located between the second and third postbasicoronal interambulacral plates; and five interambulacral zones strongly disjointed on the oral surface, separated by enlarged first post-basicoronal ambulacral plates. These characteristics coincide with the diagnosis of genus the Vaquerosella sensu Smith and Kroh (2011).…”

“…Here, we present a new clypeasteroid species with pores arranged as bands across plates as well as along sutures; sphaeridia enclosed within plate; interambulacral zones remaining biserial to apex ( Figure 4A); internal supports developed as con-centric bars ( Figure 4F) and unbranched food grooves ( Figure 2B). These characters allow us to determine its inclusion in the family Echinarachniidae sensu Smith and Kroh (2011).…”

“…The single living species of this family is Echinarachnius parma (Lamarck, 1816), a common inhabitant of shallow and interstitial marine zones along the Pacific and Atlantic of North America as well as the northwestern Pacific of Asia, from Aleutian Islands to Japan. Smith and Kroh (2011) stated that this family consists of seven valid genera: 1) Faassia Schmidt, 1971 (in Shmidt andSinyelnikova, 1971), represented by a single species from the Late Miocene deposits of western Kamchatka Peninsula, eastern Rusia; 2) Proescutella Pomel, 1883, represented only by a single species recovered in the Middle Eocene sediments at Loire Atlantique (before Loire inferieur) and Vendee, northwestern France;…”

“…3) Pseudastrodapsis Durham, 1953, that includes four Miocene-Pliocene species from Japan and the Kamchatka Peninsula, Russia (Smith and Kroh, 2011); 4) Astrodapsis Conrad, 1856, includes at least 13 extinct species from Miocene to Pliocene deposits of Pacific coast of California, USA (Conrad, 1856;Pack, 1909;Kew, 1920;Hall, 1962); 5) Echinarachnius Gray, 1825, represented by six Miocene to Pliocene species recovered in different sites of Japan (Nisiyama and Hashimoto, 1950;Morishita, 1953;Nisiyama, 1968); four species present in Middle Miocene and Pliocene deposits of Alaska, USA (Durham, 1957;Wagner, 1974); one species from Middle Miocene deposits of California (Kew, 1920), and the single Pliocene to Recent species present in both sides of North America, in the Pacific realm of Alaska and the Atlantic costs of Massachusetts, USA (Hall, 1962), and in the Northwest Pacific from Aleutian Islands via Kamchatka to Japan (Mortensen, 1948); 6) Scutellaster Cragin, 1895, from the Oligocene to Pleistocene along the Pacific coasts of North America, from Alaska to California (Wagner, 1974); and 7) Vaquerosella Durham, 1955, previously known by six nominal species from deposits of the Temblor and Vaqueros formations, in California, USA (Durham, 1955;Adegoke, 1969;among others).…”

The Ecology of Biotic Interactions in Echinoids

“…The great spider crab Hyas araneus has been observed attacking the sea urchin Strongylocentrotus in the northern polar waters, and an individual was recorded surviving more than 40 hours after extensive test damage (Wisshak and Neumann, 2020). In sand dollars, crustaceans can leave behind marginal traces because of nonlethal predation (Zinsmeister, 1980;Nebelsick, 1999). Asteroids prey on echinoids, usually consuming the entire test (Merrill and Hobson, 1970;Birkeland and Chia, 1971).…”