Raninoides danicus, Klompmaker & Martin & Hyžný & Bowman & Phillips & Portell, 2025

Raninoides danicus n. sp.

( Figs 12 View FIG ; 13 View FIG ; Appendices 1I, J; 2)

urn:lsid:zoobank.org:act:

Giulianolyreidus johnsoni ( Rathbun, 1935a) View in CoL . — Feldmann et al. 2019: 285, fig. 5.

TYPE MATERIAL. — Holotype. United States • 1 specimen; Alabama, Lowndes County, Mussel Creek roadcut ( 31°58’17”N, 86°42’15”W), ALMNH loc. 3; Clayton Formation, Pine Barren Member , lower middle NP2 nannofossil zone; Paleocene (lower Danian); ALMN-H: Paleo:21488 GoogleMaps .

Paratypes. United States • 1 specimen; same as for the holotype; ALMNH: Paleo:5919 GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21489 GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21490 GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21491 GoogleMaps • 1specimen; idem; ALMNH: Paleo:21492 GoogleMaps .

ETYMOLOGY. — danicus refers to the first species of Raninoides recognized from the Danian.

ADDITIONAL MATERIAL EXAMINED. — United States • 5 specimens; Alabama, Lowndes County, Mussel Creek roadcut ( 31°58’17”N, 86°42’15”W), ALMNH loc. 3; Clayton Formation, Pine Barren Member , lower middle NP2 nannofossil zone; Paleocene (lower Danian); ALMNH: Paleo:21493 GoogleMaps • 1specimen; idem; ALMNH: Paleo:21494 GoogleMaps • 2 specimens; idem; MMNS IP-7252 GoogleMaps • 4 specimens; idem; MMNS IP-7253 GoogleMaps • 1 specimen; idem; MMNS IP-8792 GoogleMaps • 1 specimen; idem; UF 303873 GoogleMaps .

TYPE HORIZON. — Pine Barren Member of the Clayton Formation, middle NP2 nannofossil zone, lower Danian.

TYPE LOCALITY. — ALMNH loc.3: Mussel Creek roadcut ( 31°58’17”N, 86°42’15”W), Lowndes County, Alabama, United States.

DIAGNOSIS. — Carapace length-width ratio c. 1.45 without rostrum and spines. Fronto-orbital width c. 70% of maximum width; posterior margin 70% of maximum width. Front with outer orbital spine curving inward to form straight part, lined with tubercles; intra-orbital spine surrounded by deep fissures, outer part top of spine steep-sided and lined with tubercles; outermost part rostral section of front concave, lined with tubercles. Anterolateral margin with one strong spine near outer orbital angle and directed anterolaterally, otherwise mostly straight and lined with tubercles. Sinuous band of tubercles just posterior to frontal margin. Sternite 4 longer than wide.

MEASUREMENTS. — Maximum carapace width (mm): ALMNH:Paleo:21488: 12.3, ALMNH:Paleo:5919: 14.7, ALMNH:Paleo:21490: 12.3, MMNS IP-7252.1: 15.1, MMNS IP-7253.1: 8.8.

DESCRIPTION

Carapace longer than wide (l/w ratio c. 1.45 without rostrum and spines), moderately vaulted transversely, weakly vaulted longitudinally, widest around third of length. Fronto-orbital width c. 70% of maximum width; posterior margin 70% of maximum width. Front incompletely known, but with outer orbital spine curving inward to form straight part, lined with tubercles; intra-orbital spine surrounded by deep fissures, outer part top of spine steep-sided and lined with tubercles; outermost part rostral section of front concave, lined with tubercles. Suborbital margin lined with tubercles, mostly straight except near outer orbital spines and with single deep fissure. Orbit wider than tall. Anterolateral margin with one strong spine near outer orbital angle and directed anterolaterally, otherwise mostly straight and lined with tubercles; convex transition to mostly straight and longer posterolateral margin lined with tubercles. Convex transition from posterolateral margin to posterior margin, which exhibits a slight concavity axially and is smoothrimmed. Axis of carapace with weak, rounded ridge. Carapace regions undefined, except for lateral parts of cardiac region in between concave-outward branchiocardiac grooves. Pair of posterior gastric pits in front of branchiocardiac grooves. Cuticle of dorsal carapace with widely spaced deep pits and more dense shallow pits, but with sinuous band of tubercles just posterior to frontal margin. Pterygostome with gentle ridge anteriorly, widening anteriorly, with sinuous buccal collar, with tubercular cuticle, uninterrupted transition to branchiostegite. Sternite 3 small, rounded laterally, with sharp tip and steep front; sternite 4 longer than wide, with concave lateral sides, episternites rounded; sternite 5 about equally long as wide, widening toward sternite 4, with axial groove; sternite 6 widening posteriorly, with concave posterior margin on either side of axis, with axial groove. Sternites 3-4 cuticular surface pitted but with tubercles along margins; tubercles on lateralmost parts of sternites 5 and 6 in dorsal view, and on transition from sternite 5 to 6. Pleurites 4-7 partly visible externally, smooth cuticular surface except for pleurite 4 and spines on pleurites 4-7 containing tubercles; pleurites with rims around pereiopod attachments. Coxae of maxilliped 3 curved forward, adjacent to lateral sides sternite 3. Oval attachment of cheliped pair to venter, circular for second pereiopod pair. Rostrum, pleon, and appendages not preserved.

REMARKS

Feldmann et al. (2019) ascribed three carapaces (MMNS IP-7252 [ 2 specimens] and MMNS IP-8792) to Giulianolyreidus johnsoni within Lyreidinae Guinot, 1993. The dorsal carapace is close to this species first described from the upper Danian Porters Creek Formation of Alabama ( Rathbun 1935a: pl. 17.12-17.17 [as Symethis johnsoni ]; Bishop & Whitmore 1986: fig. 1K [not 1G, 1H, 1J]; Waugh et al. 2009: fig. 11; Karasawa et al. 2014: fig. 12C, D) and later from the upper Danian Mexia Clay Member of the Wills Point Formation in Texas ( Armstrong et al. 2009: fig. 4.1-4.2 [as Macroacaena johnsoni ] [identification verified by AAK]), but the axial ridge is more prominent and the pits on the cuticular surface are larger in G. johnsoni . Moreover, the ventral side of multiple new specimens (ALMNH:Paleo:5919, ALMN-H:Paleo:21488-21490, ALMNH:Paleo:21494) and MMNS IP-8792 show marked differences, revealing an axial groove on sternites 5 and 6 ( Figs 12B View FIG ; 13A View FIG , which G. johnsoni lacks ( Rathbun 1935a: pl. 17.12). Comparable dorsal and ventral surfaces are found among Raninoidinae , such as Notosceles Bourne, 1922 , and Raninoides . The main differences between these genera involve the development of the rostrum, orbital fissures, and the outer orbital spines (diagnoses in Karasawa et al. 2014, and Schweitzer et al. 2018b), but these features are not well-preserved in the specimens from Mussel Creek. Karasawa et al. (2014) diagnosed that Notosceles exhibits short open fissures, but one specimen herein (ALMNH:Paleo:21491) exhibits fairly deep fissures ( Fig. 12F View FIG ). An additional difference we noted is that the anterolateral spine is substantially larger and more anterolaterally directed in Raninoides than in Notosceles , in which a small spine is consistently more forwardly directed across all species (see extant species and Notosceles bournei Rathbun, 1928 , from the Paleocene of Texas, Alabama, and Arkansas, see Rathbun 1935a). Many extant and fossil Raninoides have a strong anterolaterally directed spine, consistent with our specimens. This genus is diagnosed to exhibit a bifid outer orbital spine ( Karasawa et al. 2014; Schweitzer et al. 2018b), but this does not apply to all species assigned to this genus because several members have a straight plateau inward from a single spine rather than another spine (e.g., Paleocene R. borealis , extant R. crosnieri , extant R. longifrons , and extant R. personatus ). None of the fossil specimens studied here have the tip of the outer orbital spine preserved, but two specimens show a straight plateau inward in addition to the base of the outer orbital spine (ALMNH:Paleo:5919 and MMNS-IP7253.2). Thus, we assign the specimens to Raninoides with confidence.

Reasons for species separation often include the orientation, size, and location of the anterolateral spine; the development of the frontal margin and post-frontal ridge, and carapace proportions (e.g.,Collins et al. 2003; Schweitzer et al. 2006, 2012; De Angeli et al. 2009). The early Danian Raninoides danicus n. sp. differs from all other species. The stratigraphically closest species are R. borealis from the middle Paleocene (Selandian) of West Greenland and R. granulofrons from the late Campanian-early Maastrichtian of Cuba. Based on a study of the type material by AAK, R. borealis bears an anterolateral spine that may be farther from the outer orbital margin, this spine is oriented more forward, and the intra-orbital spine is more rounded. Raninoides granulofrons bears an intra-orbital spine that is more rounded on top, and the preserved base of the anterolateral spine is smaller, mentioned to be short by Vega et al. (2024).

We also compared this species to Eocene species, using the papers in which those species were first described and other papers as needed. Raninoides acanthocolus bears a shorter anterolateral spine further back on the anterolateral margin and the upper margin of the intraorbital spine slopes inward ( Schweitzer et al. 2006: fig. 2.7). Raninoides araucana bears a smaller anterolateral spine ( Philippi 1887: pl. 50.6). Raninoides budapestiniensis has an anterolateral spine further back on the anterolateral margin and a stronger postfrontal ridge ( Lőrenthey 1898: pl. 1.2). Raninoides dickersoni , only known from a venter, has a wider spine on sternite 5 ( Rathbun 1926: pl. 20.5). Raninoides fabianii apparently lacks anterolateral spines ( Lőrenthey & Beurlen 1929: pl. 4.10). Raninoides fulgidus has a proportionally smaller anterolateral spine ( Rathbun 1926: pl. 23.6; ALMNH:Paleo:5937). Raninoides glabra has the axial groove more forward onto the posterior part of sternite 4 (near the center of episternite 4) and sternite 4 is proportionally longer (see Van Bakel et al. 2012: fig. 44c, d). Raninoides goedertorum and R. notopoides exhibit smaller and more forwardly oriented anterolateral spines ( Tucker 1998: fig. 13; Hyžný & Zorn 2016: pl. 9.3). Raninoides gottschei has a smaller anterolateral spine ( Glaessner & Withers 1931: pls 20.1-2, 21.1). Raninoides perarmata and R. rathbunae have proportionally shorter sternites 4 ( Feldmann 1991: figs 2, 4; Feldmann & Schweitzer 2004: fig. 1B). Raninoides proracanthus bears a much smaller anterolateral spine ( Feldmann & Schweitzer 2004: fig. 2.8). Raninoides pulchra exhibits an anterolateral spine that is bifid near its base ( Beschin et al. 1988: pl. 4.1-3). Raninoides rioturbiensis has a longer intraorbital spine narrowing to the front and the base of the anterolateral spine is smaller ( Schweitzer et al. 2012: fig. 4). Raninoides sinuosus exhibits a smaller base of the anterolateral spine and sternite 4 is proportionally shorter ( Collins & Morris 1978: pl. 116.4-6). Raninoides slaki has a bifid intra-orbital spine and the maximum carapace width is located further posteriorly ( Squires 2001: figs 47-55). Raninoides treldenaesensis bears a smaller anterolateral spine and sternite 4 is proportionally shorter ( Collins & Jakobsen 2003: fig. 4, pl. 3.5). Raninoides vaderensis appears close but its anterolateral spine is oriented more forwardly ( Rathbun 1926: pl. 22.5; Tucker 1998: fig. 17; Gustafson 2023: figs 16-19). Raninoides washburnei has a more forwardly oriented anterolateral spine and its carapace is proportionally wider ( Rathbun 1926: pl. 22.6). We did not compare the new species to post-Eocene species because brachyuran species ranging for>32 million years are extremely unlikely and unknown to us.