Bioacoustics of Alahexapus martini

REMARKS This species is rare with only nine individuals reported herein after c. 15 years of collecting.This rarity is not primarily caused by the small size of the specimens, making them potentially more difficult to find, because many small specimens of other species were found (see above). Recently, Schweitzer (2024) ascribed four specimens to Stevea martini from a site near Streetman, Freestone County, Texas , United States , originating from the upper Danian-Selandian Wills Point Formation (see Armstrong et al. 2009 , for age). However, the tubercles on the dorsal carapace are coarser on average and more uniform in the Texan specimens based on all available specimens; sternite 4 has a wider, hexagonal-shaped extension as preserved rather than anterolaterally directed, curved spines as in A. martini n. comb. (compare Schweitzer 2024 : fig. 3.2 vs Fig. 20E ); and the pterygostome does not appear to bear the stridulating apparatus ( Schweitzer 2024 : fig. 3.6) characteristic for A. martini n. comb. ( Fig. 20L ; Feldmann et al. 2014 : pl. 3.2)though differential preservation may play a role here. Thus, the specimens from Texas may represent a different hexapodid species warranting further study.

DIAGNOSIS . — Carapace length-width ratio c. 0.67, widest about mid-length. Fronto-orbital width c. 50% of maximum carapace width. Orbits of moderate size, oval-shaped. Cervical groove widely U-shaped but diverging, fairly distinct, diminishing near orbits. Branchiocardiac grooves weaker, defining cardiac region laterally. Cuticle of carapace with densely covered fine granules.Pterygostome exhibiting stridulating apparatus with c. 15 striae. Female pleon with unfused, much wider than long somites; triangular telson with rounded tip; with gentle axial keel; pitted cuticular surface. Sternopleonal cavity of female appears to reach distal portion of sternite 3. Male pleon narrow, generally narrowing distally; telson longer than wide with rounded tip; somite 6 slightly wider than long, appears unfused, hexagonal, with rimmed lateral margins; somites 3-5 appear fused but with distinct suture marking boundaries; with pitted cuticular surface. Sternopleonal cavity of male appears to reach distal portion of sternite 4.