Caecum roederi, 2023

Raines, Bret, 2023, Caecidae (Mollusca: Gastropoda) from late Miocene exposures of the “ Imperial ” Formation in Riverside County, California, PaleoBios 40 (7), pp. 1-11 : 6-7

CAECUM ROEDERI RAINES, POWELL AND LAFOLLETTE N. SP.

FIG. 5A–I

Zoobank LSID — urn:lsid:zoobank.org:act:24C0A351-D532-4B57-9368-6B0D73A84767

Diagnosis —Teleoconch cylindrical. Surface smooth, creamy white in color. Posterior end with well-defined constriction. Septum mucronate, slightly inflated. Mucro with low rounded point. Aperture with axial rings and slight swelling followed by constriction.

Holotype — LACMIP 43085.1, LACMIP Type 14894, a complete adult shell.

Paratypes — Seven paratypes of which three are complete adult shells, LACMIP 43085.2, LACMIP Type 14895, LACMIP 43085.3, LACMIP Type 14896, UF 330224 and four are shell fragments, LACMIP 43085.4, LACMIP Type 14897, LACMIP 43085.5, LACMIP Type 14898, UF 330225 , UF 330226 .

Referred Specimens —LACMIP43085.6(1 specimen).

Occurrence — Known only from immediately above and below the Thylacodes beds near the base of section SC 3 in Super Creek, Riverside County, California .

Etymology —Named in honor of the late Mark Roeder, who was a member of the team which collected the material

Description —Protoconch and subadult stages not observed. Teleoconch, average size for genus [Tol: 1.90–2.30 mm], tubular, regularly arched [Larc: 0.60–0.82 mm; Arc: 0.18–0.22 mm], creamy white in color. Surface smooth except for 5–7 regularly spaced axial rings near aperture. Posterior [Dpe: 0.36–0.40 mm] with thick edge, rounded shoulder followed by deep, sulcus-like constriction. Septum mucronate, slightly inflated. Mucro with low rounded point positioned on dorsal margin. Aperture perpendicular [Da: 0.45–0.55 mm], with slight swelling followed by constriction. Lip smooth. Periostracum and operculum not observed.

Discussion — Caecum roederi is similar to the eastern Pacific extant species C.semicinctum de Folin, 1867 . However, C. semicinctum is much smaller with 3–4 rounded posterior rings. The only western Atlantic species that is remotely similar is C. striatum de Folin, 1868 . Although C. striatum may display a posterior constriction, it is much weaker and not always present. Caecum roederi is also larger and has apertural axial rings, which are absent in C. striatum .

Figures

Figure 5A–I. Caecum roederi Raines, Powell and LaFollette n. sp.: A–B, Holotype, LACMIP 43085.1, LACMIP Type 14894; A, profile view; B, ventral view; C, Paratype, UF 330224, ventral view; D, Paratype, LACMIP 43085.2, LACMIP Type 14895, profile view; E, Paratype, LACMIP 43085.3 Scale bar=500μm.