Navarradromites pedroartali Klompmaker, Feldmann, and Schweitzer, 2012

Klompmaker, Adiël A., Starzyk, Natalia, Fraaije, René H. B. & Schweigert, Günter, 2020, Systematics and convergent evolution of multiple reef-associated Jurassic and Cretaceous crabs (Decapoda, Brachyura), Palaeontologia Electronica (a 32) 23 (2), pp. 1-54 : 10-12

Navarradromites pedroartali Klompmaker, Feldmann, and Schweitzer, 2012

Figure 5

2012 Navarradromites pedroartali Klompmaker, Feldmann, and Schweitzer , p. 798, fig. 8.

2012b Navarradromites pedroartali Klompmaker, Feldmann, and Schweitzer ; Schweitzer et al., p. 6, fig. 5.3.

Diagnosis. Klompmaker et al. (2012, p. 796).

Material studied. Paratypes: MAB k2956, 2516, 2955, 3018, 3182; other material: 2957, 3593, 3594, 3595, UF 271729 .

Occurrence. Koskobilo quarry, northern Spain (coordinates in Google Earth: 42.88, -2.20), reef limestones of the lower upper Albian Albeniz Unit of the Eguino Formation (Klompmaker, 2013a; López-Horgue and Bodego, 2017).

Dimensions. (In mm) MAB k3591: max. length excl. rostrum but incl. epigastric swellings (L)=-, max. width (W)=9.9; MAB k3593: L=-, W=2.7; see Klompmaker et al. (2012, table 2) for more measurements.

Description. Referral is made to Klompmaker et al. (2012, p. 799). New details of orbital structure: lateral side of orbits usually show a wide fissure or re-entrant (MAB k2516, 2955, 2956, 3182, 3591, 3593, and 3595); anterolaterally oriented outer orbital spine wider than tall in cross-section (MAB k3182, 3593); lower orbital margin does not project beyond upper orbital margin (MAB k3593, 3591); and rectangular lower orbital margin exhibits a weak concavity in dorsal view (MAB k3593, 3591). Rostrum in frontal view with small, downturned, axially indented projection for some large specimens (MAB k3018, 3182, 3594) or with single small triangle in small specimens (MAB k2955- 2957).

Remarks. As Eodromites cristinarobinsae sp. nov. and Navarradromites pedroartali can look very similar to one another for incompletely preserved specimens, differences are highlighted here. The outer orbital spines break off easily and so do the rostral spines, which make them appear almost identical to specimens of E. cristinarobinsae sp. nov. When well-preserved, these orbital spines tend to be more pronounced in N. pedroartali . The downturned, indented projection of the rostrum in frontal view for large specimens of N. pedroartali appears absent in E. cristinarobinsae sp. nov. for similar-sized specimens, where this character is either pointed or straight [MAB k2513, 2626, 2638 ( Figure 4F )]. Lastly, the lateralmost part of the cervical groove in dorsal view tends to bend forward more so than in Eodromites cristinarobinsae sp. nov. (see Klompmaker et al., 2012; Figures 4 , 5 ).

A previous article (Klompmaker et al., 2012, p. 796) found placement in homolodromiids unlikely because “the carapace of the homolodromiids has its widest part typically in the posterior [or central] part of the carapace, [the former of] which is the part that is typically narrowest in Navarradromites .” Comparisons to homolodromiids deserve a more extensive discussion because of multiple striking similarities. The frontal structure with two rostral spines in dorsal view and the anterolaterally projected outer orbital spines are very reminiscent of extant (e.g., Guinot, 1995; Martin et al., 2001; Ng and McLay, 2005; Lemaitre and Tavares, 2014) and fossil (Förster et al., 1985; Feldmann, 1993; Schweitzer and Feldmann, 2010d, for Homolus auduini Eudes-Deslongchamps, 1835 ) homolodromiids. Additionally, the concavity or opening in the orbital rim in lateral view in Navarradromites (but see MAB k3591) is also seen in extant homolodromiids (e.g., Báez and Martin, 1989; Martin et al., 2001; Ng and McLay, 2005; Lemaitre and Tavares, 2014). However, a spine on the lower orbital margin that is often present in homolodromiids (Martin, 1990; Guinot, 1995; Schweitzer et al., 2004; Schweitzer and Feldmann, 2010d; Lemaitre and Tavares, 2014) is absent in Navarradromites . Furthermore, based on a limited number of specimens, the orbits of homolodromiids appear shallower usually (Förster et al., 1985, p. 344; Báez and Martin, 1989, figure 2A; Martin, 1990, figure 2B but see figure 5B; Feldmann et al., 1993, figure 27.2; Lemaitre and Tavares, 2014, figure 5C) than in Navarradromites . Together with these differences in the orbital region, the different overall outline and the close similarity to Eodromites in shape and groove pattern suggest that placement within Goniodromitidae remains best supported. The frontal structure with a bifid rostrum and anterolaterally oriented spines is a remarkable example of convergent evolution of Navarradromites toward members of Homolodromiidae , for which this type of frontal structure is characteristic.

Figures

FIGURE 4. Specimens of the crab Eodromites cristinarobinsae sp. nov. from the mid-Cretaceous (lower upper Albian) reef limestones of Koskobilo, northern Spain. A-C, dorsal views (holotype MGSB78750, paratype UF 271883, and paratype MAB k3592, resp.). D-F, frontal views (MGSB78750, UF 271883, and MAB k2638, resp.). G, H, right- and left-lateral views (MAB k2950 and MAB k2953, resp.). I, oblique view of lateral part of orbital structure with fissure (MAB k2626); upper orbital margin incomplete; height figure ~1.0 mm. A, D, G, and H colored dark and subsequently coated with ammonium chloride prior to photography; from Klompmaker et al. (2012, figure 5B, H, J, and K, reproduced with permission). Those images are not published under the terms of the CC-BY license of this article. For permission to reuse, please see Klompmaker et al. (2012). Scale bar width equals 1.0 mm.

FIGURE 5. Specimens of the crab Navarradromites pedroartali Klompmaker et al., 2012, from the mid-Cretaceous (early late Albian) of Koskobilo, northern Spain. A-C, dorsal views (holotype MGSB77711, MAB k3593, and MAB k3591, resp.). D, F, frontal views showing somewhat different rostral tips (MAB k3018 and MAB k3591, resp.). E, K, right-lateral views (MAB k3593 and MAB k3591, resp.). G, H, views of orbital structure with fissure laterally (MAB k3591 and paratype MAB k3182, resp.); height G ~1.0 mm. I, frontal view of damaged upper orbital projection that is wider than tall (paratype MAB k3182). J, lower orbital margin (upper orbital margin is not complete), width figure ~0.5 mm (MAB k3593). A and D colored dark and subsequently coated with ammonium chloride prior to photography; from Klompmaker et al. (2012, figure 8D, I, reproduced with permission). Those images are not published under the terms of the CC-BY license of this article. For permission to reuse, please see Klompmaker et al. (2012). Scale bar width equals 1.0 mm.