Mexorchestia Wildish & LeCroy 2014
Creators: name: Lowry, J. K.
name: Myers, A. A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Talitridae
Mexorchestia

description: Mexorchestia Wildish & LeCroy, 2014
Mexorchestia Wildish & LeCroy, 2014: 561.
“ Tethorchestia ”.— LeCroy, 2011: 757.
Type species. Mexorchestia carpentaria carpentaria Wildish & LeCroy, 2014, original designation.
Included species. Mexorchestia includes 1 species: M. carpenteri Wildish & LeCroy, 2014.
Category. Mascupod.
Ecological type. Beach-hopper.
Habitat. Found on bare white sand and from wrack consisting of macroalgae and mangrove litter (Wildish & LeCroy 2014).
Diagnostic description (male). Based on Wildish & LeCroy (2014).
Head. Antenna 2 peduncular articles slightly incrassate. Mandible left lacinia mobilis 5-cuspidate (tiny fifth cusp), or 4-cuspidate. Labium without inner lobes. Maxilliped palp article 2 with distomedial lobe; article 4 reduced, button-shaped.
Pereon. Gnathopod 1 sexually dimorphic; subchelate; posterior margin of carpus and propodus each with lobe covered in palmate setae; propodus anterior margin with 2 groups of robust setae, ‘subtriangular’ with welldeveloped posterodistal lobe, palm transverse; dactylus? simplidactylate. Gnathopod 2 subchelate; propodus palm acute, evenly rounded, without palmar sinuses; without large distal sinus; without proximal spine or thumb defining palm; dactylus attenuated distally. Pereopods 3–7 dactyli bicuspidactylate. Pereopod 4 dactylus amplidactylate, thickened proximally with notch midway along posterior margin. Pereopod 6 shorter than pereopod 7; not incrassate; basis expanded; male merus and carpus not expanded. Pereopod 7 not incrassate; basis broadly expanded; posterior margin smooth or minutely serrate margin with numerous small robust setae, posterodistal lobe absent; merus slightly expanded distally, subtriangular, anterior margin slightly convex; carpus unexpanded, subrectangular; propodus broad; length 6.7 × width, male with large distal tuft of setae. Oostegites (female) setae with spatulate tips.
Pleon. Pleopods all slightly reduced. Uropod 1 peduncle distolateral robust seta absent; exopod without marginal robust setae; endopod with marginal robust setae in 1 row. Uropod 2 exopod with marginal robust setae in 1 row; endopod with marginal robust setae in 2 rows. Uropod 3 ramus shorter than peduncle. Telson apically incised, with 7 to at least 10 robust setae per lobe.
Remarks. Wildish & LeCroy (2014) discuss the very close relationship between Mexorchestia and Tethorchestia. They distinguish the genera on the relative development of the distolateral robust seta on the peduncle of uropod 1, the shape of the female gnathopod 2 basis and the shape of the oostegites.
The slightly incrassate second antenna and large distal tuft of setae on the propodus of pereopod 7 and the distally attenuated dactylus of gnathopod 2 distinguish Mexorchestia and Tethorchestia from all other platorchestiine genera. There are several other characters separating these genera. Mexorchestia has a slightly incrassate antenna 2 (incrassate in Tethorchestia); pereopod 6 merus expanded in Mexorchestia (not expanded in Tethorchestia), pereopod 7 basis without a posterodistal lobe in Mexorchestia (present in Tethorchestia) and oostegites with spatulate tips in Mexorchestia (simple in Tethorchestia).
Distribution. USA: Florida. Caribbean Sea, Yucatan Peninsula to Belize (Wildish & LeCroy 2014).
description: Published as part of Lowry, J. K. & Myers, A. A., 2022, Platorchestiinae subfam. nov. (Amphipoda, Senticaudata, Talitridae) with the description of three new genera and four new species, pp. 1-53 in Zootaxa 5100 (1) on page 27, DOI: 10.11646/zootaxa.5100.1.1, http://zenodo.org/record/6127681