Protomunida Beurlen, 1930

Hryniewicz, Krzysztof, Amano, Kazutaka, Bitner, Maria Aleksandra, Hagström, Jonas, Kiel, Steffen, Klompmaker, Adiël A., Mörs, Thomas, Robins, Cristina M. & Kaim, Andrzej, 2019, A late Paleocene fauna from shallow-water chemosynthesis-based ecosystems, Spitsbergen, Svalbard, Acta Palaeontologica Polonica 64 (1), pp. 101-141 : 124

Genus Protomunida Beurlen, 1930

Type species: Galathea munidoides Segerberg, 1900 ; Paleocene (middle Danian), Faxe Formation, Denmark .

Species included: Protomunida munidoides ( Segerberg, 1900) ;? P. pentaspina Beschin, Busulini, and Tessier in Beschin et al., 2016; P. primaeva ( Segerberg, 1900) ; P. spitzbergica ( Gripp, 1927) .

Original diagnosis (translated from Beurlen 1930: 373).— Protomunida is characterized by a smooth, triangular rostrum without teeth, and with two spines near its base. Shape of the carapace and ornamentation as in Galathea . Protomunida thus occupies a pronounced intermediate position between Galathea and Munida .

Emended diagnosis.—Carapace excluding rostrum longer than wide, subrectangular; with three-pronged rostrum, of which one major, moderately narrow, flattened spine on the axis and two smaller accessory spines; forwardly directed spine at outer orbital angle; row of spines or tubercles on epigastric regions; epibranchial regions with tubercles dorsally and spines laterally; other ornamentation oriented transversely; fairly smooth, non-depressed area posterior to cardiac region.

Remarks.—Beurlen (1930: 373) erected Protomunida with Protomunida munidoides ( Segerberg, 1900) as the type species, but he also put Munida primaeva Segerberg, 1900 , and Galathea spitzbergica Gripp, 1927 , in this genus, which was generally not followed by subsequent workers (e.g., Collins and Jakobsen 1994; Jakobsen and Collins 1997; Schweitzer and Feldmann 2000; De Angeli and Garassino 2002; Schweitzer et al. 2010; Robins 2013; Beschin et al. 2016; Klompmaker et al. 2016; Robin et al. 2017; but see Müller and Collins 1991). We here place Munida primaeva (for confirmed images of this rare species see Segerberg 1900: pl. 7.6; Jakobsen and Collins 1997: pl. 2.8; Klompmaker and Boxshall 2015: fig. 1D; Damholt et al. 2010: 22) and Galathea spitzbergica (see below) in Protomunida again after 88 years based on the close similarity to the type species including the three-pronged rostrum, the spine on the outer orbital angle, the oblique ridge of tubercles on the epigastric regions, the overall ornamentation, the fairly smooth, non-depressed area posterior to the cardiac region, the tubercles on the epibranchial regions, and the overall groove pattern. We consider placement of Protomunida pentaspina Beschin, Busulini, and Tessier in Beschin et al., 2016, in Protomunida (see Beschin et al. 2016) provisional because the rostrum is poorly preserved but is wider at the posterior part than in all other congenerics. Other characters match those of Protomunida , but also of many species of Eosadayoshia Beschin, Busulini, and Tessier in Beschin et al., 2016, and Sadayoshia Baba, 1969 . Whether? P. pentaspina has more spines on the anterior carapace region than P. munidoides (see Beschin et al. 2016) cannot be fully confirmed. However, the posterior side of the lateral margin of? P. pentaspina has more spines than that of P. munidoides . Differences include the cardiac region, which is rectangular in P. spitzbergica and? P. pentaspina but more triangular in P. munidoides and P. primaeva , the epibranchial regions showing also ridges in addition to tubercles in P. munidoides and? P. pentaspina , and the wider central rostral spine of P. spitzbergica with tubercles not seen in P. munidoides and P. primaeva . The cervical groove of P. primaeva is more V-shaped than the U-shaped groove in the other species. Given that Protomunida has barely been used since its erection in 1930 and many new genera now classified within the Munididae have been erected without proper comparison to Protomunida , a renewed comparison is warranted. Agononida Baba and de Saint Laurent, 1996 , has a very narrow central, needle-like rostral spine (rather than a flattened central projection) and spines around the meta-/urogastric regions not seen in Protomunida . Anoplonida Baba and de Saint Laurent, 1996 , and Anomoeomunida Baba, 1993 , have smaller accessory rostral spines and epibranchial regions with transverse ridges rather than tubercles/spines. Babamunida Cabezas, Macpherson, and Machordom, 2008 , Cervimunida Benedict, 1902 , Crosnierita Macpherson, 1998 , Enriquea Baba, 2005 , and Raymunida Macpherson and Machordom, 2000 , have a narrow central, needle-like rostral spine. Austromunida Schweitzer and Feldmann, 2000 , has a much narrower central, needle-like rostral spine and no tubercles on the epibranchial regions, the latter of which also applies to Cretagalathea Garassino, de Angeli, and Passini, 2008 . The genera Bathymunida Balss, 1914 , Heteronida Baba and de Saint Laurent, 1996 , Neonida Baba and de Saint Laurent, 1996 , Onconida Baba and de Saint Laurent, 1996 , Plesionida Baba and de Saint Laurent, 1996 , and Tasmanida Ahyong, 2007 , all bear a strong forwardly directed ridge ending in a spine occupying the mesogastric region. Hendersonida Cabezas and Macpherson, 2014 , has a granular carapace surface rather than transverse ridges. Juracrista Robins, Feldmann, and Schweitzer, 2012 , has a much wider rostrum overall, and especially the central projection is wider. Munida Leach, 1820 (type species) and Torbenella Baba, 2008 , have a narrow central, needle-like rostral spine and ridges on the epibranchial regions. Paramunida Baba, 1988 , differs in that transverse ridges are indistinct and the rostrum is relatively short. Unlike Protomunida , Pleuroncodes Stimpson, 1860 , shows the epimeral sutures dorsally and has a narrow central, needle-like rostral spine. Raymunida has a straighter row of epigastric spines. Sadayoshia and Eosadayoshia bear five rostral spines rather than three. Setanida Macpherson, 2006 , appears to have a cardiac region reaching the posterior margin and lacks a row of epigastric spines/tubercles. Differences from Valamunida Klompmaker and Robins gen. nov. are described below. Thus, we conclude that Protomunida is a distinct genus within the Munididae .