Balhuticaris is a genus of extinct bivalved (referring to the carapace) hymenocarine arthropod that lived in the Cambrian aged Burgess Shale in what is now British Columbia around 506 million years ago.
[1][2][3] The hymenocarines were an order of primitive mandibulates, the arthropod group that includes crustaceans, insects, myriapods and their relatives, that lived throughout the Cambrian period.
[1] Balhuticaris was the largest bivalved arthropod in the fossil record, beating the previous holders of this title Nereocaris exilis and Tuzoia.
[1] Eoredlichia Kunmingella Kunyangella Perspicaris recondita Perspicaris dictynna Canadaspis Branchiocaris Tokummia Nereocaris exilis Fibulacaris Pakucaris Nereocaris briggsi Balhuticaris Odaraia Jugatacaris Fuxianhuia Chengjiangocaris Erjiecaris Loricicaris Plenocaris Clypecaris Ercaicunia Chuandianella Waptia Pectocaris Pauloterminus
Cladogram of Hymenocarina, following Izquierdo-López and Caron, (2024), which recovered Balhuticaris within Odaraiidae:[4]Tuzoia Perspicaris Pectocaris Loricicaris Tokummia Branchiocaris Plenocaris Ercaicunia Clypecaris Pauloterminus Canadaspis Waptia Chuandianella Vermontcaris Odaraia Jugatacaris Fibulacaris Pakucaris Balhuticaris Nereocaris This hymenocarine most likely engaged in a fast-paced nektonic (free swimming) lifestyle.
Examples being the presence of a tripartite caudal rami, a feature only found in hymenocarines,[1][2] and that the carapace goes ventrally beyond the legs, which would have heavily impaired this arthropods ability to crawl on the ocean floor.
Modern day arthropods of a similar size like lobsters, stomatopods, and giant isopods are mainly scavengers or predators.
[1] This is not unheard of, as many other free-swimming arthropods like anostracans,[7] pelagic trilobites like the Telephinids,[8] xiphosurans,[1] and other odaraiid hymenocarines, like Odaraia and Fibulacaris swam in inverted positions.
[10] Dozens of creatures have been preserved at this site including lobopodians, stem-group and total-group Arthropoda, worms, primitive chordates, echinoderms, sponges, as well as other animal groups.