Eodromites rotundus, 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 : 11-13

Eodromites rotundus n. sp.

Figures 2.2-3, 6

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Diagnosis. Small sized species (max. carapace length about 4 mm). Carapace is longer than wide (width 0.80-0.88 of length). Lateral borders are smooth, narowing posteriorly. Outer orbital spine is distinct. The AtC distance is very short (0.26-0.30x RtC distance). Rostrum is long and wide, rounded. Augenrest is barely longer than wide (1.1x), bordered, deep, subtriangular, asymmetric along the horizontal axis, with elevated posterior angle. Projection of orbital margin intercepts longitudinal axis at about a 50 degree angle. Hepatic tubercles are FIGURE 6 . Eodromites rotundus n. sp. 1. Paratype, rostrum – dorsal view (3992, Ogrodzieniec). 2. Paratype, rostrum – dorsal view (6270, Ogrodzieniec). 3. Groups of hepatic pits (hp) on the hepatic region (2237, Bzów). 4. Carapace - paratype, cervical pits (cp) (3992). 5. Carapace - paratype, cervical pits (6270). 6. Augenrest, anterior view (619, Ogrodzieniec). 7. Holotype - augenrest, anterior view (6271, Ogrodzieniec). 8. Holotype, lateral view (6271). Scale bars equal 1 mm .

faint. Hepatic pits are arranged in groups. Three pairs of symmetric pits on the upper orbital margin and on the epibranchial region are absent. Epibranchial region is much shorter than the branchial region.

Etymology. A new species name derives from a Latin word “rotundus ” – rounded. It refers to rounded rostrum, characteristic to that species.

Type material. Holotype: I-F / MP/6271 /1599/12, type locality: Ogrodzieniec, age: Lower and Middle Oxfordian.

Paratypes. I-F / MP/3992 /1533/08; I-F / MP/6270 / 1599/12, locality: Ogrodzieniec, age as for the holotype; I-F / MP/1842 /1517/08, locality: Bzów, age: Middle Oxfordian.

Additional material. Poland, Bzów: I-F / MP /1677/ 1517/08; I-F / MP /2237/1528/08; I-F / MP /2509/1528/ 08; I-F / MP /6370/1619/14. Niegowonice: I-F / MP / 193/1495/08. Ogrodzieniec: I-F / MP /619/1502/08; IF/ MP /663/1502/08; I-F / MP /685/1502/08; I-F / MP / 4061/1533/08; I-F / MP /4165/1533/08; I-F / MP /4287/ 1534/08; I-F / MP /6274/1599/12.

Dimensions. The biggest specimen (663) is 3.81 mm long and 3.35 mm wide, the smallest (685) is 1.92 mm wide.

Description of material. The carapace is convex, longer than wide (width 0.80-0.88 of the length); especially elongated is the anterior part of the carapace. Lateral borders are smooth, narrowing posteriorly. The outer orbital spine is distinct and sharp. The AtC distance is very short (0.26-0.30 of the RtC distance) (Figures 2.2, 3).

The rostrum is long and broad, rounded, directed downwards. Axial groove is deep, not reaching the anterior margin of rostrum (Figure 6.1-2).

The augenrest is only slightly longer than wide (1.1x), bordered and deep, subtriangular, ansymmetric along the horizontal axis, with an elevated posterior angle. The anterior groove is absent. The suborbital margin extends beyond the upper orbital margin. Projection of an orbital margin intercepts the longitudinal axis at about a 50 degree angle (Figures 2.3, 6.6-7).

Hepatic tubercles and pits are very faint. Groups of hepatic pits are best visible in specimens 663, 1842 and 6270 (Figure 6.3).

Epigastric regions are small. Mesogastric region is bottle shaped, rather poorly delimited. Two delicate scars on both sides of a small incision in the middle of posterior border of the mesogastric region are less visible here than in other studied species. The urogastric region bears a small tubercle. The cardiac region is slightly convex, with two tubercles in its anterior and one in the posterior part.

The epibranchial region is more convex than the branchial region but the difference is not as conspicuous as in E. grandis . The branchial region is much longer than the epibranchial region (Figures 2.2, 6.4-5).

The cervical groove is deeper than the branchio-cardiac groove, which is very faint in the middle part. Postcervical groove is also poorly visible.

Remarks. Structures like hepatic tubercles, groups of hepatic pits, epigastric regions or mesogastric region are weakly visible in this small species, but present and recognizable under the sidelight.

The carapace of E. rotundus n. sp. is narrowing posteriorly as in E. grandis , but it is relatively longer. It is shorter and much smaller than E. aequilatus . Eodromites rotundus n. sp. has the lateral borders smooth, unlike both these species compared. Also the AtC distance is shortest in E. rotundus . The rostrum is longer than in E. grandis and broader than in E. aequilatus . The augenrest is shorter than in E. grandis but longer than in E. aequilatus , with a similarly elevated posterior angle. The hepatic tubercles are faint as in other species. The groups of hepatic pits are weaker than in E. grandis and E. aequilatus . Epibranchial region of E. rotundus n. sp. is more convex than the branchial region but the difference is not as conspicuous as in E. grandis .