Eodromites hyznyi, 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 : 13-15

Eodromites hyznyi n. sp.

Figures 2.2-3, 7

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Diagnosis. Small sized species (width about 3 mm), carapace is longer than wide. Lateral borders are almost parallel, smooth. AtC distance is very short (0.23x the RtC distance). Rostrum is long, strongly narrowing anteriorly. Augenrest is short (1.2x longer than wide), bordered, subtriangular and asymmetric along the horizontal axis, with elevated posterior angle. Upper and suborbital margins are smooth. Projection of orbital margin intercepts longitudinal axis at about a 50 degree angle. Hepatic tubercles are absent. Groups of hepatic pits are shallow and faint. There is only one of three pairs of symmetric pits present, a very shallow I pair on the upper orbital margin. There are two shallow grooves running parallel to lateral sections of the branchio-cardiac groove.

Etymology. Species’ name is dedicated to Matúš Hyžný, a specialist of fossil decapods.

Type material. Poland: Holotype: I-F / MP/4973 / 1543/09, type locality: Niegowonice , age: Middle to Upper Oxfordian (upper Elisabethae Subzone to the upper Wartae Subzone).

Paratypes. I-F / MP/1067 /1508/08, locality: Niegowonice, age as the holotype; I-F / MP/3468 /1533/ 08, locality: Bzów, age: Middle Oxfordian (Transversarium Zone).

Additional material. Niegowonice: I-F / MP /4558/ 1534/08; I-F / MP /5062/1543/09.

Dimensions. Width of carapace ranges from 2.72 mm to 3.39 mm. A total length of carapace cannot FIGURE 7. Eodromites hyznyi n. sp. 1. Holotype, suborbital margin marked with an arrow (4973, Niegowonice). 2. Paratype, cervical pits (cp) (3468, Bzów). 3. Paratype, lateral view, groove parallel to branchio-cardiac groove marked with an arrow (3468). 4. Paratype, augenrest, I – pit on the upper orbital margin (3468). Scale bars equal 1 mm.

be defined precisely because posterior border of the carapace is not preserved in any specimen.

Description of material. The carapace is longer than wide, flattened. Lateral borders are smooth, slightly narrowing posteriorly. Outer orbital spine is present. The AtC distance is small (0.23 of the RtC distance) (Figures 2.2, 3).

The rostrum is long, strongly narrowing anteriorly, sharply ended. The axial groove is deep, reaching to the anterior edge of rostrum. The rostrum is best preserved in specimen 4973 (Figure 7.1). The anterior groove is absent.

The augenrest is longer than wide (length 1.2 of the width), asymmetric along the horizontal axis, with an elevated posterior angle. Upper and suborbital margins are smooth; suborbital margin extends beyond the upper orbital margin. The projection of orbital margin intercepts longitudinal axis at about a 50 degree angle. Details of augenrest are best visible in specimens 1067, 3468 and 4973 (Figures 2.3, 7.4).

Epigastric regions are rounded, flattened. The mesogastric region is bottle-shaped, with distinct border in anterior and posterior part, and faint in the middle. There are two delicate scars on both sides of a small incision in the middle of posterior border of this region. In front of them there is a pair of similar, smaller scars. The urogastric region bears a small, indistinct tubercle.

The cervical pits are rounded (Figure 7.2). Hepatic tubercles are absent. Groups of hepatic pits are very faint, best visible in specimen 1067. There is only one of the three pairs of symmetric pits present, a very shallow I pair on the upper orbital margin (Figure 7.4).

The cardiac region is flattened, with two tubercles in its anterior part and one in the posterior part. The epibranchial region is more convex and much shorter than branchial region.

The cervical groove is deep. The branchio-cardiac groove is deep in lateral parts (parallel to cervical groove), and very faint in the medial part. There are two shallow grooves running parallel to the lateral sections of the branchio-cardiac groove (Figure 7.3). The postcervical groove is deeper in lateral parts, shallower in the middle; it merges with the branchio-cardiac groove.

Remarks. The carapace of Eodromites hyznyi n. sp. is relatively longer and less narrowing posteriorly than in E. grandis . Lateral borders are smooth in contrast to E. grandis and E. aequilatus . The AtC distance is relatively shorter than in other three species. Rostrum is here relatively longest, and narrow as in E. aequilatus . The augenrest is longer than in E. aequilatus and E. rotundus n. sp., and shorter than in E. grandis . The groups of hepatic pits are not as well visible as in other mentioned species. In contrast to other species, the hepatic tubercles are absent.