Parathaumatelson Gurjanova, 1938

Krapp-Schickel, Traudl, 2006, Thaumatelsonine Stenothoids (Crustacea, Amphipoda). Part 2, Zootaxa 1165, pp. 1-31 : 25-27

Parathaumatelson Gurjanova, 1938

Gurjanova, 1938, 277, 387. Barnard, 1972b,158. Barnard, 1974b,108.

Type species, Metopella nasica (Stephensen) .

Characters

Antenna 1 article 1 nasiform process; accessory flagellum absent. Mandible palp absent, maxilla 1 palp 2 articles, maxilla 2 plates fused, inner plate short, between tandem­ and riding position. Gnathopod 1, 2 subchelate, scarcely different in size and shape, palm shorter than posterior margin, which is parallel to anterior one; gnathopod 1 merus lobed and produced, gnathopod 2 merus short. Pereopods 3–7 dactyli with comb­row of setae. Pleonsegment 3 lacking dorsal process. Urosomite 1 with dorsal fold, vaulting over urosomite 2 and part of telson, compress with carena. Urosomite 2 triangular, urosomite 3 shortened; suture between second and third urosomite not clearly visible. Telson vaulted dorsally, apex obtuse and upturned, like minute spoon; partly concealed under the long dorsal process of first urosomite.

Remarks

When Schellenberg 1931 selected Pseudothaumatelson patagonicum as type of his genus Pseudothaumatelson , he included Metopella nasica Stephensen. Gurjanova created the genus Parathaumatelson for Metopella nasica , but J.L. Barnard 1964 synonymised again the genera. J.L. Barnard (1972b, 158) revived Parathaumatelson stressing the following characters: mandibular palp (one long article in Pseudothaumatelson , lacking in Parathaumatelson ), accessory flagellum (not observed in both genera, however discussed in J.L. Barnard 1972b), size and shape of gnathopods (similar in Parathaumatelson , dissimilar in Pseudothaumatelson ). By the latter character as well as the nasiform article 1 of the first antenna Parathaumatelson resembles Chucullba but has very different third uropods and telson. I surmise that the complex of the genera Pseudothaumatelson , Thaumatelsonella (both treated in part 1, Krapp­Schickel 2000) and Parathaumatelson all have a similar structure of urosome and telson and are closely related, having the most plesiomorph characters of all thaumatelsonids. The "fleshy" three­dimensional telson is described in different ways according to different techniques of dissection and preparation of slides.

Parathaumatelson nasicum ( Stephensen, 1927)

Figure 4 c

Metopella nasica Stephensen, 1927 , 309–311, fig. 7.

Parathaumatelson nasica Gurjanova, 1938 , 387. Barnard, 1964, 71. 1972b, 158–160, fig. 90. 1974b, 108.

Pseudothaumatelson nasica J.L. Barnard, 1964 , 71.

Material examined

Type material. CM­CR­3199 Holotype and syntype Auckland, Carnley harbour, under stones, 29.11. 1914 2 spec. 1.5mm; CM­CRU­7493 syntype Auckland, Carnley harbour, 3.12. 1914 1 spec. 2mm; CM­CRU­3200 Auckland, Carnley harbour, 25.11. 1914 1 female ovigerous, 2.5mm. ­ SIM 4 ind. alcohol, Nr. 149528. AMS (Snares I., SA­820, 10/ 1/1975, among algae, lower littoral rocks) 1 ind. slide, 2 in alcohol, Nr. P048535.

Diagnosis

Antenna 1<antenna 2, antenna 1 article 1 strongly nasiform swollen, article 2 short; antenna 2 article 3 trapezium­shaped; mandible palp lacking; gnathopod 1, 2 subchelate, similar; pereonite 4 enlarged, equal in length to pereonites 2+3. Urosome very compressed, with dorsal carina. Thick fold of urosomite 1 vaulting over urosomite 2 and part of telson, length of urosomite 1 dorsally about the same as length of antenna 1 article 1 dorsally. Uropod 1, 2 peduncle subequal to blade­shaped rami, dorsal margins of peduncles and rami crenulated; uropod 3 ramus long and blade­shaped; insertion of peduncle hidden by translucid, but strong integument, linking or nearly "bandaging" urosomite 1 ventrally with insertion of telson. Telson inserted three­dimensionally, not excavated but dorsally convex, proximally coalesced with urosomite 3.

Distribution New Zealand and Snares Islands.

Ecology Among algae on lower littoral rocks.

Figures

FIGURE 4. Antatelson walkeri (Chilton). a) habitus; b) urosomites and telson. c) Parathaumatelson nasicum (Stephensen) urosomites with flange and telson.