Carolinapecten murdockensis druidwilsoni Waller, 2018
WALLER, T. R. 2018. Systematics and biostratigraphy of Chesapecten and Carolinapecten (Mollusca: Bivalvia: Pectinidae) in the upper Miocene and Pliocene "lower Tamiami Formation" of southwestern Florida. Bulletin of the Florida Museum of Natural History, 56 (1): 1-47, figs. 1-11. [p. 28, figs. 9E-9H]
2018 Carolinapecten murdockensis druidwilsoni Waller, 2018
T. R. Waller, 2018, figure 9.
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«Zoobank Nomenclatural Act.— E4BBCA70-540D-4590-883B-C993170047C0.
Diagnosis.— Strongly right-convex Carolinapecten with right umbo projecting above dorsal margin and left valve much less convex than right; dorsal margins of auricles of right valve with shallow folds barely projecting above outer-ligament grooves; disks with 16−18 ribs squared in early ontogeny, high and rounded later, without secondary costellae; right anterior auricle with three or four radial costae, most commonly three, and moderately deep byssal notch with active ctenolium persisting throughout ontogeny. Description.— Shell of medium size, with maximum observed height of 80 mm but most specimens no higher than 65 mm, strongly right convex with right valve moderately inflated and commonly over twice the convexity of left valve; disk gapes absent or narrow; height and length about equal or with length slightly the greater; convexity of articulated shell about 35% of shell height. Total hinge length 55–70% of shell length, with anterior and posterior hinge lengths about equal; dorsal folds of right auricles weakly developed, not projecting far above outer-ligament grooves. Disks with 16–18 ribs, most commonly 17, ribs high with deeply incised interspaces on both valves, wider than interspaces on right valve, narrower on left; rib profiles rectangular to subrectangular on right valve, becoming more rounded but remaining high in late ontogeny; ribs of left valve more distinctly rectangular in profile with more flattened crests in early ontogeny; lateralmost ribs of each valve weaker than others but persisting without subdivision throughout ontogeny. Commarginal growth lines closely spaced in rib interspaces, disappearing or weakly developed on rib crests; disk flanks sloping and rounded on right valve, narrower and steeper on left, lacking radial striae but crossed by commarginal growth lines. Byssal notch of right valve remaining moderately deep with rounded apex throughout ontogeny; active ctenolium persisting into late ontogeny, with byssal fasciole slightly depressed but narrowly raised along suture and crossed by commarginal growth lines; byssal sinus of left anterior auricle very shallow; margins of posterior auricles shallowly outwardly convex, with overall trend varying from perpendicular to dorsal margin to forming an acute angle; right anterior auricle with three or four radial costae, most commonly three; left anterior auricle with six to nine radial costae, posterior auricles with very weak costae, about five or six. Hinge dentition of right valve consisting of strong resilial teeth extending laterally nearly parallel to hinge line; dentition of left valve consisting of strong infradorsal and infraresilial teeth. Umbonal cavity extending beneath resilifers of both valves, more so on right valve than on left; auricular denticles well developed at distal ends of ridges on shell interior at ventral edge of auricles. Pallial line well inset from ventral margin at about one-third height of valve. Umbonal inner foliated calcite layer extending ventrally to about mid-adductor level. Etymology.— Named for the late Druid Wilson, paleontologist of the U.S. Geological Survey, whose extensive collections from the southwestern Florida Peninsula have been the primary source of data for the present study. Type material and measurements.— Holotype: USNM 716594, closed articulated shell, Ht 48.1 mm, L 49.0 mm, convexity of articulated shell 17.9 mm (Fig. 9E–H). Type locality.— USGS 26913, Sarasota County, Florida. “Cocoplum Waterway, Port Charlotte-Collingswood. D. Wilson, M. Hunter, J. Banks, T. Waller, and W. Blow, Feb. 26, 1968.” Other material.— About 100 specimens (single valves plus pairs of matching valves) from six localities in the Port Charlotte area. Comparisons.— Carolinapecten murdockensis druidwilsoni resembles Ca. corpulentus in being right-convex and having a majority of specimens with only three costae on the right anterior auricle, but differs in having a much less inflated left valve and subrounded ribs. Carolinapecten murdockensis murdockensis, in contrast to Ca. murdockensis druidwilsoni, is nearly equiconvex and has more sharply squared rib profiles and commonly four costae on the right anterior auricle. Carolinapecten murdockensis parawatsonensis differs from other subspecies of Ca. murdockensis in having fairly broad disk gapes and lateralmost ribs that subdivide near the distal margin. All of the subspecies of Ca. murdockensis differ from Ca. eboreus watsonensis in having less deeply folded dorsal margins of the right-valve auricles, a deeper byssal notch, a more ontogenetically persistent active ctenolium, and higher ribs. Occurrence.— Port Charlotte area, west of Murdock: Cocoplum Waterway: USGS 26913; Auburn Waterway: USGS 22256, USGS 269061, USGS 26908; Jupiter Waterway: USGS 26916. Distribution.--Carolinapecten murdockensis druidwilsoni occurs in biozone PZ2 (see Biostratigraphy section) in beds interpreted as being in the lower part of the Bayshore Clay Member of the lower Tamiami Formation of Hunter (1968). Remarks.— Carolinapecten murdockensis druidwilsoni is associated with broad-ribbed Ecphora in the Ecphora gardnerae complex (Fig. 4D–F), non-auriculate oysters in the Mansfieldostrea compressirostra complex (Fig. 4G−H), and Chesapecten middlesexensis hunterae (Fig. 3A–K). At its type locality on the Cocoplum Waterway, Ca. murdockensis druidwilsoni occurs in a barnacle-hash coquina consisting mainly of fragmented Fistulobalanus klemmi Zullo, 1984 (Fig. 4I−J), a barnacle heretofore known only from the lower Yorktown Formation in North Carolina, but inferred herein to be present also in the upper Miocene (see Biostratigraphy section). Also abundant is an undescribed species of Argopecten, with all valves having very worn surfaces (Fig. 4B−C).» THOMAS RICHARD WALLER, 2018
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