Alphacheles, Klompmaker & Martin & Hyžný & Bowman & Phillips & Portell, 2025

Klompmaker, Adiël A., Martin, P. George, Hyžný, Matúš, Bowman, Andrew R., Phillips, George E. & Portell, Roger W., 2025, Systematics, biodiversity, and paleoecology of an early Danian decapod crustacean assemblage from Alabama, United States, Geodiversitas 47 (13), pp. 577-622 : 580-581

publication ID

https://doi.org/10.5252/geodiversitas2024v47a13

publication LSID

urn:lsid:zoobank.org:pub:F5144147-C045-48FD-8128-7F822CDE6B18

DOI

https://doi.org/10.5281/zenodo.17243626

persistent identifier

https://treatment.plazi.org/id/F77987B8-FFB6-FF9B-11E0-CE77AE82F955

treatment provided by

Plazi

scientific name

Alphacheles
status

gen. nov.

Genus Alphacheles n. gen.

urn:lsid:zoobank.org:act:

TYPE SPECIES. — Callianassa zeta Rathbun, 1936 ( Callianassa alpha Rathbun, 1935a ; non Callianassa alpha Stenzel, 1935 ), by present designation.

ETYMOLOGY. — The genus name is a combination of “alpha ”, referring to the homonymous species name Callianassa alpha , and “cheles” meaning “claw”. Gender: masculine.

DIAGNOSIS. — As for the type species.

REMARKS

Shortly after the description of Callianassa alpha Rathbun, 1935a , it was revealed that the name had already been used by Stenzel (1935) for yet another fossil ghost shrimp assigned to Callianassa . A rectification was published in the following year, renaming C. alpha to C. zeta Rathbun, 1936 .

Callianassa zeta differs from all known extant and extinct ghost shrimp taxa by its tuberculate area (“densely punctate excrescence” sensu Rathbun [1935a]; “triangular patch of granules” sensu Feldmann et al. [2019]) at the base of the fixed finger which is present at the outer and inner lateral surfaces. This character has been considered a diagnostic feature of this species ( Rathbun 1935a; Feldmann et al. 2019). Its taxonomic significance is herein elevated to the genus level, and hence a new genus is proposed to accommodate this species.

So far, only propodi and dactyli are known for Alphacheles zeta ( Rathbun, 1936) n. comb. Most specimens represent major claws, whereas in one case also a minor claw is identified ( Fig. 5O View FIG ). Their morphology is rather close to that of extant species of Gourretia View in CoL and Paragourretia View in CoL , based on which the new genus is classified within the family Ctenochelidae View in CoL . Nevertheless, the familial placement of Alphacheles n. gen. should be considered preliminary until more complete material is found. Alphacheles n. gen. shares with the above-mentioned genera the following set of characters: major cheliped propodus distinctly longer than high and subrectangular in outline, relatively long fingers exceeding half of the propodus palm length, and dactylus occlusal surface with simple dentition (cf. Le Loeuff & Intès 1974; Sakai 2002, 2004; Ngoc-Ho 2003). These characters are shared also with Cretagourretia, an exclusively fossil genus known from the Early Cretaceous (Albian) of Spain. This set of characters mentioned above is rarely seen in other ghost shrimp families ( Poore & Ahyong 2023). As mentioned above, Alphacheles n. gen. differs from all ghost shrimp genera known to date by the presence of a tuberculate area at the base of the fixed finger. It differs also from yet another exclusively fossil ctenochelid genus, Ahazianassa , from the Late Cretaceous (Maastrichtian) of Japan. Additionally, Alphacheles n. gen. possesses a more elongate palm than Ahazianassa does.

Besides Callianassa alpha, Rathbun (1935a) described also “ C. alpha var.” from the Upper Eocene Jackson Group of Mississippi. A new variety of C. alpha is based on a single incomplete propodus and a pleon found at the same locality. Because the isolated propodus does not appear to show a densely tuberculate area at the base of the fixed finger, “ C. alpha var.” is not considered closely related to Alphacheles zeta n. comb. Given the large temporal separation of c. 25 million years, these specimens might represent a new species, but a restudy of the specimens is needed.

Kingdom

Animalia

Phylum

Arthropoda

Class

Malacostraca

Order

Decapoda

InfraOrder

Axiidea

Family

Palaeoxanthopsidae

GBIF Dataset (for parent article) Darwin Core Archive (for parent article) View in SIBiLS Plain XML RDF