Journal of Paleontology, 92(2), 2018, p. 170–182 Copyright © 2017, The Paleontological Society 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.65


Appraisal of the fossil record of Homarus (nephropid lobster), with description of a new species from the upper Oligocene of Hungary and remarks on the status of Hoploparia


Dale Tshudy,1 Matúš Hyžný,2 Alfréd Dulai,3 and John W.M. Jagt4


1Department of Geosciences, Edinboro University of Pennsylvania, Edinboro, PA 16444, U.S.A. ⟨dtshudy@edinboro.edu⟩ 2Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava,


Slovakia; Department of Geology and Paleontology, Natural History Museum, Burgring 7, 1010 Vienna, Austria ⟨hyzny.matus@gmail.com⟩ 3Department of Palaeontology and Geology,HungarianNatural HistoryMuseum, Ludovika tér 2, 1083Budapest,Hungary ⟨dulai.alfred@nhmus.hu⟩ 4Natuurhistorisch Museum Maastricht, 6211 KJ Maastricht, the Netherlands ⟨john.jagt@maastricht.nl⟩


Abstract.—The fossil record of the clawed lobster genus, Homarus, is appraised. The taxonomic history of Homarus and Hoploparia is summarized, and a list of species recognized for each is provided. A tabulation of all fossil species of the family Nephropidae permits assessment of nephropid species diversity through time. A new species of Homarus, H. hungaricus, is recorded from the upper Oligocene (Chattian) Mány Formation at Mány, northern Hungary. The species is known by a single specimen consisting of a partial cephalothorax, a pleon minus telson, and partial chelipeds. Homarus is now known by two extant species (H. americanus and H. gammarus) and six fossil taxa, one of Early Cretaceous (Albian; H. benedeni) and five of Cenozoic age (H. hungaricus n. sp., H. klebsi, H. lehmanni, H. morrisi,and H. percyi). The new fossil Homarus differs from modern congeners in aspects of carapace and pleon ornamentation and, especially, cutter claw shape. This is the fourth Oligocene occurrence of a nephropid species; all are Homarus and all are from Western Europe. Homarus makes its appearance in the fossil record in the Early Cretaceous (Albian) and then is not known again until the Paleogene, despite the fact that nephropid lobsters in general are well known from the Late Cretaceous. Nephropid lobsters are better known from the Cretaceous than from the Cenozoic. Both raw species numbers and numbers corrected (normalized) for epicontinental sea coverage show that shelf-dwelling nephropid lobsters were most diverse during the Late Cretaceous.


Introduction


The clawed lobster family Nephropidae Dana, 1852, consists of 56 Recent and 79 fossil species, arrayed in 19 genera (10 Recent, five fossil, and four both fossil and extant). The Nephropidae has a fossil record extending back to the Lower Cretaceous (Valanginian, ca. 139.8–132.9 Myr). The clawed lobster genus Homarus Weber, 1795 is known


by two Recent and six fossil species. In modern oceans, Homarus is represented by theAmerican lobster,H. americanus Milne Edwards, 1837, and the European lobster, H. gammarus (Linnaeus, 1758). These species are morphologically very similar, differing only in the spinosity of the rostrum; H. americanus having a spine or two on the underside, and H. gammarus lacking these (Beard and McGregor, 2004). The two are capable of artificial breeding (Hauge, 2010). Six fossil species of Homarus recognized herein, all European, give the genus a fossil record extending back to the Early Cretaceous (ca. 100 Ma). To some extent, the extant Homarus resembles the extinct


Hoploparia M’Coy, 1849. Placement of species in these genera has been the subject ofmuch discussion. The separateness of, and differences between, Homarus and Hoploparia have been long debated and are still not resolved. Many authors have considered


Homarus and Hoploparia to be distinct (Mertin, 1941; Glaess- ner, 1969; Feldmann, 1974; Aguirre-Urreta et al., 1991; Tshudy, 1993; Feldmann and Crame, 1998; Tshudy and Sorhannus, 2003; Ilyin, 2005; Feldmann et al., 2007; De Grave et al., 2009; Schweitzer et al., 2010; Karasawa et al., 2013; and others). Woods (1931), Van Straelen (1936), and Stenzel (1945) viewed the two genera as synonymous. The current view is to separate them. In our opinion, there is not a single character that can be used alone to distinguish the two genera. We use a total evidence approach in drawing generic boundaries—and, even then, with difficulty. Not surprisingly, in cladistic analyses, Homarus and Hoploparia plot out as sister groups (Tshudy, 1993; Tshudy and Babcock, 1997; Ahyong, 2006; Karasawa et al., 2013). Hoploparia is most readily distinguished from Homarus


(Fig. 1) by the ventral extension of the branchiocardiac groove (absent on Homarus) and the granulation of the exoskeleton (almost entirely absent on Homarus). In addition, the majority of Hoploparia display an antennal carina, whether short or long (absent on Homarus), as well as postantennal spines (absent on Homarus). Homarus lacks sculpture and orna- mentation on its pleonal terga and pleura (some Hoploparia possess these). Claws of Homarus are much broader than those of nearly all Hoploparia (except for Hoploparia antarctica Wilckens, 1907).


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