Healdia mckittrickensis Tarnac & Forel & Nestell & Nestell & Crasquin 2021, sp. nov.

Healdia mckittrickensis Crasquin sp. nov.

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Fig. 4A–C

Diagnosis

A species of Healdia with a stocky carapace, a massive overlap of LV on RV, thick posterior spines; a curved ridge extends in front of the spines.

Etymology

In reference to the ‘McKittrick Canyon’ Member, Bell Canyon Formation, Guadalupe Mountains, West Texas, where this species has been discovered.

Material examined

Holotype USA • complete carapace, (Fig. 4A); Guadalupe Mountains, West Texas, ‘ McKittrick Canyon’ Member, Bell Canyon Formation, MKCS1 section, sample GM5; Capitanian, Middle Permian; MNHN.F. F63365.

Paratype USA • 1 incomplete carapace (DB and PVB of LV are missing), (Fig. 4B); Guadalupe Mountains, West Texas, Williams Ranch Member, Cutoff Formation, Quarry section, sample GM1; Roadian, Middle Permian; MNHN.F. F63366.

Additional material USA • 1 right valve; Guadalupe Mountains, West Texas, ‘ McKittrick Canyon’ Member, Bell Canyon Formation, MKCS1 section, sample GM5; Capitanian, Middle Permian; MNHN.F F63367 • 3 complete carapaces; Guadalupe Mountains, West Texas, Williams Ranch Member, Cutoff Formation, Quarry section, samples GM1, GM4; Roadian, Middle Permian; MNHN.F. F63473.

Dimensions

L= 224–807 µm; H =139–489 µm.

Description

Carapace stocky, subtriangular to ovoid in lateral view; important overlap of RV by LV with maximum along PDB; dorsal margin of LV regularly arched with Hmax at posterior ⅓ of L; dorsal margin of

RV with Hmax at mid-L; AB with maximum of convexity located slightly below Hmax; VB slightly concave at both valves; PB large and close to vertical; presence of two posterior spines quite large, their bases are linked by an intra-spines tenuous ridge; in front of the spines, presence of a curved ridge, more developed than the intra-spines one; surface smooth.

Occurrence

Samples GM1, 4 (GM5), Quarry section, Williams Ranch Member, Cutoff Formation, Roadian; MKCS1 section, sample GM5, ‘McKittrick Canyon’ Member, Bell Canyon Formation, Capitanian; Middle Permian, Guadalupe Mountains, West Texas, USA (this work).

Remarks

Healdia mckittrickensis sp. nov. has an unique morphology. The general outline is reminiscent of Healdia subtrangula Kotschetkova, 1959 from the Kazanian (Roadian) of Bashkiria, SW of the Ural Mts (Kotschetkova 1959) but H. mckittrickensis sp. nov. has a less triangular lateral outline with thicker spines.