Iphiculus eliasi, Hyžný, Matúš & Gross, Martin, 2016

Hyžný, Matúš & Gross, Martin, 2016, A new iphiculid crab (Crustacea, Brachyura, Leucosioidea) from the Middle Miocene of Austria, with notes on palaeobiogeography of Iphiculus, Zootaxa 4179 (2), pp. 263-270 : 266-268

Iphiculus eliasi sp. nov.

( Figs 2 A, 3A–E, 4A–C)

Diagnosis. Carapace transversely subovate in outline, widest at level of posteriormost anterolateral spine; lateral margins bearing 6 short triangular spines; dorsal carapace surface covered evenly with large rounded tubercles: hepatic region with tubercle, gastric region with 3 pairs of tubercles, branchial region with 3 tubercles.

Etymology. The species name is dedicated to Eliáš, son of the first author.

Material examined. Holotype: near-complete carapace UMJGP Inv.No. 75.612, max. length, 15.7 mm; max. width, 19.0 mm ( Figs 3 A–D). Paratype: near-complete carapace UMJGP Inv.No. 75.613, max. length, 13.0 mm (preserved portion); max. width, 17.2 mm; Fig. 3 E). Additional specimen: carapace fragment UMJGP Inv.No. 211339; Fig. 4 A–C).

Description. Small carapace; transversely subovate in outline; slightly wider than long, widest at midlength, at level of posteriormost anterolateral spine; dorsal surface moderately convex in both directions. Front not projected, slightly raised, narrow, not well preserved, presumably bilobed. Orbits small, concave, anteriorly directed. Lateral margins bearing 6 short triangular spines, anterolateral margin with 4 spines, posterolateral margin with 2 spines; corners between posterolateral, posterior margins pointed; posterior margin straight, narrow. Dorsal surface of carapace evenly covered with many large, densely packed granules, nearly identical in size (if cuticular surface preserved) or with round concave pustules (if cuticular surface not preserved). Carapace surface covered evenly with large rounded tubercles: hepatic region with 1 tubercle, gastric region with 3 pairs of tubercles, branchial region with 3 tubercles. Carapace grooves absent in anterior carapace portion, well developed in posterior carapace portion. Gastric region large, indistinctly demarcated with grooves. Cardiac region ovate in outline, strongly arched. Branchial regions broad. Intestinal region narrow without large spines. Sternum, pleon, pereiopods unknown.

Occurrence. The species is known only from its type locality at Wetzelsdorf ( Austria).

Remarks. Iphiculus eliasi sp. nov. is closest to the extant I. convexus in terms of the morphology of the dorsal carapace. The latter species, however, has a relatively wider carapace closer to the anterior half and possesses more large round tubercles on the dorsal carapace, especially on the hepatic and gastric regions ( Fig. 2 A versus Fig. 2 B). Another extant species, I. spongiosus , differs from I. eliasi sp. nov. by the presence of large anterolateral spines and the possession of dorsal carapace tubercles which are more projected outwards (Ng et al. 2008: fig. 79). Similarly, all fossil species of Iphiculus so far known, i.e. I. granulatus Morris & Collins, 1991 , I. miriensis Morris & Collins, 1991 , and I. sexspinosus Morris & Collins, 1991 , have well-developed anterolateral spines ( Morris & Collins 1991: figs 15, 14 and 17, respectively) which are absent in I. eliasi sp. nov.

Iphiculus eliasi sp. nov. also resembles some Typilobus species. Typilobus kishimotoi Karasawa, 1998 , from the Miocene of Japan has similarly shaped carapace outline and possesses large rounded tubercles on the dorsal surface; but the tubercles are fewer than in I. eliasi sp. nov. ( Fig. 3 A vs. Karasawa 1998: fig. 2). Additionally, T. kishimotoi has two longitudinal ridges behind the median sulcus of the frontal region ( Karasawa 1998: fig. 2.2b), a feature that is absent in the new species ( Figs. 2 A, 3A, 3C).

One specimen of Iphiculus eliasi sp. nov. (UMJGP 21.1339) exhibits partial cuticle degradation on the preserved portion of the carapace ( Fig. 4 A–C). It suggests rather complex internal structure of the tuberculation of leucosioids; tubercles are expressed differently in various cuticular layers. It was already noted that taphonomic aspects of the cuticle preservation in fossil crabs may have major impact on taxonomical evaluation of the characters such as carapace ornamentation (e.g. Feldmann & Portell 2007; Klompmaker et al. 2015). Therefore, only large rounded tubercles present also on the specimen without preserved cuticle ( Fig. 3 A–D) are considered of taxonomical importance herein.

Vía (1941) reported an “ Iliinae , Ebaliinae ?” from the Middle Miocene of Catalonia, Spain. His figure ( Vía 1941: pl. 10, fig. 75) clearly represents a leucosioid crab with striking similarities to Iphiculus eliasi sp. nov. Müller (1993: figs 5M–N) refigured the specimen in greater detail (although still insufficient for closer comparison) and assigned it questionably to the leucosiid genus Randallia Stimpson, 1857 sensu lato (see Galil 2003). Re-examination of the specimen is needed to resolve its affinities.

Figures

FIGURE 2. Fossil and extant Iphiculus. A, Iphiculus eliasi sp. nov., holotype UMJGP 75.612 in dorsal view (dry and uncoated); B – D, Iphiculus convexus Ihle, 1918, ZRC 2009.0462 (male specimen from Vanuatu) in dorsal (B), posterior (C), and posterodorsal view (D). Photos in B – D by P. K. L. Ng.

FIGURE 3. Type material of Iphiculus eliasi sp. nov. A – D, holotype UMJGP 75.612 in dorsal (A), posterodorsal (B), frontal (C), and posterior view (D); E, paratype UMJGP 75.613 in dorsal view. Specimens were coated with ammonium chloride prior the photography. All specimens to scale.

FIGURE 4. Additional material of Iphiculus eliasi sp. nov. A – C, UMJGP 21.1339 with partially degraded cuticular surfaces (B – C). Specimen in A was coated with ammonium chloride prior the photography.