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| Apristurus ovicorrugatus White, O'Neill, Devloo-Delva, Nakaya & Iglésias, 2023 DOI: 10.1111/jfb.15415 |
Abstract
Apristurus ovicorrugatus, a new species of deepwater catshark, is described from northwestern Australia. Unique egg cases belonging to an unknown species of Apristurus prompted a more detailed investigation of Apristurus specimens off northwestern Australia. One specimen previously identified as A. sinensis collected off Dampier Archipelago was found gravid with a single egg case. Removal of this egg case confirmed that this species was responsible for producing the unique egg cases previously recorded. The egg cases of this species have strong T-shaped longitudinal ridges on the dorsal and ventral surfaces which are unique in the genus Apristurus. The ridges most closely resemble those present in Bythaelurus canescens from South America, but are larger and always T-shaped. The holotype is closest morphologically to A. sinensis but differs in having a medium brown buccal cavity (vs. jet black), ridged egg cases (vs. smooth egg cases), fewer intestinal spiral valve turns and larger pectoral fins. The holotype is also similar, and closest on a molecular level, to A. nakayai with which it shares a unique synapomorphic character, the white shiny iris (apomorphic within the genus). A late-term embryo removed from an egg case superficially resembled the holotype except in having two parallel rows of enlarged dermal denticles on the dorsolateral predorsal surface. Recent nomenclatural changes to the genera Apristurus and Pentanchus are discussed and challenged. This study highlights the important contribution that egg case morphology has on oviparous elasmobranch taxonomy.
Keywords: Apristurus brunneus group, discovery, egg cases, genetics, new species, Pentanchidae
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| Lateral view of Apristurus ovicorrugatus n. sp. holotype (CSIRO H 3161-01, adult female 467 mm LT): (a) fresh; (b) preserved |
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| Dorsal view of trawled egg cases of Apristurus ovicorrugatus n. sp. (CSIRO H 8056-01); top egg case contained a 68.7 mm late-term embryo. Scale bar = 10 mm |
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| Egg case of Apristurus ovicorrugatus n. sp. (CSIRO H 9058-01) attached to octocoral (Thouarella sp.) |
Apristurus ovicorrugatus n. sp.
Synonymy: Apristurus sp.?: Human, 2011: 199, Figures 1, 6 (northwestern Australia);
Apristurus sinensis (in part): Last & Stevens, 2009: 195 (northwestern Australia in part).
Vernacular: Ridged-egg Catshark.
Diagnosis: A small Apristurus species with the following combination of characters: eyes with shiny white iris (when fresh); head moderately long and relatively narrow, head length 23.8% LT, interorbital space 6.4% LT; snout moderately elongate, preoral length 10.0% LT, preorbital length 10.9% LT; mouth wide, its width 9.5% LT; pelvic–anal space 5.9% LT; anal fin large, base length 15.2% LT, posterior margin 11.5% LT; prepectoral length relatively long, about 21.1% LT; labial furrows long, not confined to mouth corners, uppers longer than lowers (3.8 vs. 2.4% LT); no enlarged denticles on upper or lower caudal fin; duodenum of intestine moderately sized, 15 intestinal spiral valves; 35 monospondylous centra; 33 precaudal-diplospondylous vertebrae; precaudal centra 68; females mature by 467 mm LT; egg case small (50.4–60.6 mm long), with 5–7 strong T-shaped ridges on dorsal and ventral surfaces.
Etymology: Name derived from a combination of the Latin ovi (egg; genitive singular of ovum) and corrugatus (corrugated) in allusion to the corrugated egg cases that this species exhibits which are unique for the genus Apristurus. The name ovicorrugatus is treated as an adjective.
William T. White, Helen L. O'Neill, Floriaan Devloo-Delva, Kazuhiro Nakaya and Samuel P. Iglésias. 2023. What came first, the Shark or the Egg? Discovery of A New Species of Deepwater Shark by investigation of Egg Case Morphology. Journal of Fish Biology. DOI: 10.1111/jfb.15415
phys.org/news/2023-05-species-shark-unique-egg-cases.html
