Alkaidia

Lore & Background

The fossilized remains of Alkaidia were first described by paleontologists Daniel B. Blake and Robert Reid, III in a 1998 publication describing Albian-aged starfish fossils from north-central Texas. Over 50 specimens, some complete and others fragmentary, from the Washita Group were assigned to the new genus and species Alkaidia sumralli. The generic name references Alkaid, a star in Ursa Major, and the specific name honors Colin Sumrall, who discovered and prepared some specimens, including the holotype. The holotype, a complete specimen (1786TXI), was found in deposits of the Del Rio Formation at Waco Dam Quarry and placed in the Texas Memorial Museum. Additional fragments from the same locality and from the Paw Paw Formation were designated as paratypes.

A second species, Alkaidia megaungula, was described in 2020 by paleontologists Timothy A. M. Ewin and Andrew S. Gale based on material from the Taba Starfish Bed of the Barremian-aged Taboulouart Formation in Morocco, purchased from commercial fossil collectors. The specific name means 'large hoof' in Greek, referencing the large terminal ossicle resembling a hoof. The studied specimens are well-preserved and represent numerous individuals of various growth stages, allowing an ontogenetic series to be shown.

Reader's Guide

Alkaidia is significant as an extinct genus of sea stars that provides insight into Cretaceous marine life in the western Tethys Ocean. The genus was first described in 1998, with the type species A. sumralli known from over 50 specimens from Texas, including complete and fragmentary fossils from the Washita Group. The discovery of a second species, A. megaungula, in Morocco in 2020 extended the geographic and temporal range of the genus to the Barremian stage. The well-preserved Moroccan material, representing multiple growth stages, allowed an ontogenetic series to be documented, offering rare data on the development of these ancient echinoderms. The specific name of A. megaungula, meaning 'large hoof,' highlights a distinctive anatomical feature. The genus is named after the star Alkaid, reflecting a common practice of linking fossil taxa to celestial bodies. The holotype of A. sumralli is housed in the Texas Memorial Museum, and the species honors Colin Sumrall for his contributions to specimen collection and preparation.

Did You Know?

• Alkaidia is named after Alkaid, a star in the constellation Ursa Major.
• The type species A. sumralli honors Colin Sumrall, who discovered and prepared some specimens.
• The second species A. megaungula means 'large hoof' in Greek, referencing its large terminal ossicle.
• Fossils of A. megaungula were purchased from commercial fossil collectors.