Pterognathia tuatara, Sterrer, 2006

Sterrer, Wolfgang, 2006, Gnathostomulida from the Otago Peninsula, southern New Zealand, Zootaxa 1172, pp. 1-19 : 11-13

Pterognathia tuatara n. sp.

(Fig. 5.1–5.7, 6.1–6.3)

Type material Holotype one adult from sample SI 16, in squeeze preparation, NZNM W.1534. Further material: Three juveniles and one anterior fragment from the same sample.

Etymology After the tuatara, an ancient reptile endemic to New Zealand.

Diagnosis

Colorless, slender Pterognathia (body index 43.75) with slender rostrum (index 5.17). Jaws 18.00 µm long, with 4–7 dorsal and 7–14 ventral teeth. Basal plate plump crescentshaped, 4.20 µm long and 10.40 µm wide (index 0.41), with 27.2 fine teeth on median half of rostral edge. Sperm with weakly spiralized head­middlepiece 23 µm long, and tail 9 µm long.

Description

Organization and behavior. Body colorless­transparent. The only adult was 1750 µm long and 40 µm wide at U 20 (body index 43.75). Rostrum slender and pointed, 155 µm long and 30 µm wide at U 6.9 (rostrum index 5.17). The posterior end tapers into a pointed tail region.

Digestive tract. In the adult the mouth was at U 6.5. Basal plate crescent­shaped, 4.20 µm long and 10.40 µm wide (index 0.41), with one pair of longitudinal fibulae and slightly knob­shaped, rostrally curved lateral wings. The median half of its straight rostral edge is set with 24–30 (27.2) fine, sharp teeth, which seem to be arranged in two horizontal rows.

Jaws 18.00 µm long, with slender, curved rostral apophyses and a crescent­shaped symphysis. The jaws are bipartite, with 4–7 semi­circularly arranged teeth on the dorsal part, and 7–14 linearly arranged teeth on the ventral part.

Male system. About 350 µm long, the paired testes extend from U 65.7 to U 85.7. The paired vasa deferentia seemed to merge prior to opening into a ventral male pore situated at about U 97. The only sperm measured (Fig. 5.6) was 32 µm long, and composed of a faintly spiralized head­middlepiece 23 µm long, and a tail 9 µm long.

Female system. A mature egg, 200 µm long, extended from U 37.1 to U 48.6.

Discussion

This species shares much of its mouth part architecture with P. sorex Sterrer, 1969 ; P. ctenifera Sterrer, 1970 ; and P. crocodilus Sterrer, 1991 . In addition to bipartite, manytoothed jaws all four species have a rod­ to crescent­shaped basal plate whose dorsorostral edge is set with teeth. There are consistent differences, however, that set the new species apart. The basal plate of P. tuatara has the shape of a plump crescent (as expressed in the high basal plate index of 0.41) whereas in the other three species it is a slender sickle ( P. crocodilus , index 0.34) or rod ( P. ctenifera , index 0.31; P. sorex , index 0.25–0.29). Furthermore, teeth are distributed over half of the basal plate width in P. tuatara whereas they occupy less width in the other species. Jaws are very similar in this species foursome except that those of P. ctenifera stand out not only as the smallest (13.00 µm) but also as having short, stubby rostral apophyses that point latero­caudally, rather than mediocaudally (i.e., towards the symphysis) as in the other three species.