Eodromites guenteri, Starzyk, 2015

Starzyk, Natalia, 2015, Reappraisal of the primitive crab Eodromites, with description of three new species from European localities (Decapoda: Brachyura: Goniodromitidae), Palaeontologia Electronica 35 (7), pp. 1-19 : 15-16

Eodromites guenteri n. sp.

Figures 2.2-3, 8

zoobank.org/ 8E719474-23ED-4C8B-9DA4-226DB961B870

Diagnosis. Large-sized species (length of the holotype 11.96 mm), longer than wide (width 0.88x length). Lateral borders are smooth. AtC distance is long (0.37x RtC). Rostrum is short and rounded, with an incision in the middle. Augenrest is very long (1.75x longer than wide), symmetric along the horizontal axis. Projection of orbital margin intercepts longitudinal axis at about a 60 degree angle. Anterior groove is very faint. Hepatic tubercles are faint; groups of hepatic pits are well visible. Three pairs of symmetric pits; I-III are present. There are two tubercles between the cervical and hepatic groove.

Etymology. Species’ name is dedicated to Günter Schweigert (Staatliches Museum für Naturkunde, Stuttgart, Germany), a world-known palaeontologist and a specialist of fossil decapods.

Type material. Holotype: SMNS61668 /4. Type locality: Blaubeuren , Sonderbucher Steige , Massenkalk formation ( Germany). Age: Upper Kimmeridgian, Eudoxus Zone.

Dimensions. Length of the holotype is 11.96 mm, width is 10.57 mm.

Description of material. The carapace is moderately flattened, relatively long (width 0.88 of the length). Lateral margins are smooth, narrowing posteriorly. The outer orbital spine is distinct and sharp. The AtC distance is longer than in E. grandis but shorter than in E. aequilatus (0.37 of the RtC distance) (Figures 2.2, 3).

The rostrum is short and rounded, narrower than in E. grandis , slightly directed downwards, with an incision in the middle. An axial groove is very shallow, not reaching the anterior margin of rostrum (Figure 8.1).

The augenrest is longer than in other studied species (1.75x longer than wide), bordered, and symmetric along the horizontal axis. The upper and suborbital margins are not well preserved; the suborbital margin extends beyond the upper orbital margin (Figures 2.3, 8.7). An anterior groove is very faint. A projection of orbital margin intercepts the longitudinal axis at about 60 degree angle.

Cervical pits are rounded, distinct; hepatic tubercles are faint. Three pairs of symmetric pits are present: one pair on the upper orbital margin and two pairs on the epibranchial region, II next to the cervical groove and III next to the branchio-cardiac groove. There are two tubercles between the cervical and the hepatic groove (Figures 2.2, 8.1, 8.3).

Epigastric regions are small, rounded. Mesogastric region is bottle shaped; only its posterior margin is well visible. There are delicate scars on both sides of a small incision in the middle of posterior border of the mesogastric region; and in front of them a pair of nodular, smaller scars is present. The urogastric region bears a small, indistinct tubercle (Figure 8.2, 8.6). The cardiac region is slightly flattened, with two tubercles in its anterior and one in the posterior part.

The epibranchial region is flattened as the branchial region and also short.

The cervical and branchio-cardiac grooves are deep in lateral parts and shallower in medial parts. The branchio-cardiac groove is almost not visible posteriorly to the cardiac region. The postcervical groove is weakly visible, deeper in lateral parts; it merges with the branchio-cardiac groove.

Remarks. The species most similar to E. guenteri n. sp. is E. grandis , which differs in the AtC distance being shorter and in the absence of pits I-III. In contrast to other congeners, E. guenteri n. sp. has rostrum incised in the middle. This species has also the longest augenrest of all studied species. The groups of hepatic pits are weaker than in E. aequilatus but more distinct than in remaining species.

FIGURE 8. Eodromites guenteri n. sp., holotype 1. Rostrum, dorsal view, pit on the upper orbital margin (I) (SMNS61668/4, Blaubeuren). 2. Mesogastric region, cervical pits (cp), hepatic tubercles (ht), tubercles between cervical and hepatic groove (hct). 3. Pits: I - on the upper orbital margin, on the epibranchial region next to the cervical groove (II) and the branchio-cardiac groove (III). 4. Carapace. 5. Groups of hepatic pits on the hepatic region (hp). 6. Mesogastric region, cervical pits (cp), hepatic tubercles (ht). 7. Augenrest, anterior view. 8. Carapace, lateral view. Scale bars equal 1 mm.