Paleochicoreus Merle 2024, n. gen.

Genus Paleochicoreus Merle, n. gen. (Fig. 2) urn:lsid:zoobank.org:act: 3E5850A7-582D-48BF-B126-BA40739DDC00 TYPE SPECIES. — Chicoreus (Phyllonotus) initialis Vokes, 1990. United States, Texas, middle Eocene (Bartonian) (Fig. 2A, B). SPECIES INCLUDED. — Murex packardi Dickerson, 1915, Washington (United States), middle Eocene; Chicoreus (Phyllonotus) initialis Vokes, 1990, Texas (United States), middle Eocene (Lutetian); Pterynoyus newtoni Eames, 1957 [new name for “ Pteropurpura ” cf. tricarinatus Newton, 1922], Nigeria, middle Eocene, Fig. 2C; Murex diderrichi Vincent, 1913 [?synonym of Murex camerunensis Oppenheim, 1904], Angola, Cameroon, late Paleocene-early Eocene; Murex bicostatus Deshayes, 1835, France, middle Eocene (Bartonian) (Fig. 2D, E). ETYMOLOGY. — Name formed by palaiós (meaning old in ancient Greek) and Chicoreus. DIAGNOSIS. — Biconic and middle-sized shell with Chicoreus shape. Well marked primary cords. Spire: IP (infrasutural ramp), P1 to P3 (convex part of whorl). Last whorl: IP, P1 to P6 (convex part of whorl), P6 not atrophied, ADP, MP and ABP (siphonal canal). Nodulose protovarices on early whorls. Three varices with one or two intervarices on succeeding whorls. Varices slightly winged on last whorl. No cord spine even on P1. Shoulder sinus very short. Aperture ovate with strong internal denticles within outer lip: ID, D1 to D6. Columellar lip smooth. Parietal callus and anal notch present. Aragonite microstructure. REMARKS During the Eocene several species of Paleochicoreus Merle, n. gen. appeared in Eastern Pacific (North American coast), Western Atlantic (North American coast) and Eastern Atlantic (West Africa and Europe), which have been attributed in the literature to Pterynotus Swainson, 1833 or Chicoreus Montfort, 1810 (Eames 1957; Vokes 1971, 1990; Merle et al. 2011 as? Chicoreus). With Chicoreus, they share a biconic shell, medium length of siphonal canal, trivaricate morphology, nodulose protovarices, an anal notch, and a parietal callus. However, these features are also shared with the genera Naquetia Jousseaume, 1880, Phyllonotus Swainson, 1833 and Chicomurex Arakawa, 1964. Paleochicoreus Merle, n. gen. differs from these three genera by having a smooth columellar lip. For example, according to Vokes (1990), Chicoreus (Phyllonotus) initialis (herein Paleochicoreus initialis n. comb.) (Fig. 2A, B) is most similar to members of Phyllonotus, because of developed internal denticles of the outer lip, but it lacks the derived characters of Phyllonotus (rugae and expanded parietal shield). Paleochicoreus newtoni (Fig. 2C) possesses an expanded varical flange, like that in Paleochicoreus initialis n. comb., but this character is lacking in many Chicoreus species. Members of Chicoreus (Triplex) and C. (Rhizophorimurex) also bear similarities with those of Paleochicoreus Merle, n. gen., but they lack an expanded varical flange, their internal denticles are reduced or missing, and they often develop spiny processes. Chicoreus (s.s.), which is rather similar to C. (Triplex), differs by having a labral groove spine placed between P4 and P5 (Merle et al. 2011: fig. 37A, B), lacking in Paleochicoreus Merle, n. gen. Species such as Paleochicoreus initialis n. comb. and P. newtoni represent ideal ancestral lineages for Chicoreus, Chicomurex or Phyllonotus (Vokes 1990) but cannot readily be assign to one of these branches. This comment is true for other species attributed here to Paleochicoreus Merle, n. gen. Here, we figure and give a new description of the holotype of P. bicostatus (Deshayes, 1835), n. comb. This very rare species has not been found subsequent to its original description. Information given hereunder is based on the holotype retrieved from the collections of the École des Mines, Lyon.