Zachos—Paleocene echinoids
unequal, outside pore larger than interior, somewhat oblique, separated by small bead; replaced by single pores near margin, at least internally. Pores in petals elongate, conjugate, outer pores more elongate than inner. Peristome in anterior third of test, semicircular in outline, lipped. Labrum short, contacts both ster- nal plates. Peripetalous fasciole not deeply indented, parallel to anterior petal for about half their length, then straight to tips of posterior petals, lateral fasciole indistinct and poorly developed. Tubercles small aborally, larger along margins of ambulacral depressions; larger andmore scattered orally; posterior ambulacra naked orally.
Additional material.—MMNS 5301, from the Clayton Forma- tion, Lowndes County,
Alabama.MMNS 7095,MMNS7096.1, and MMNS 7096.2 from Clayton Formation, Shell Creek Park on Alabama River, Wilcox County, Alabama.
Occurrence.—Clayton Formation, Dr. A.J. Parkes farm, 5 miles south of Ellaville, Schley County, Georgia (exact locality unknown). Clayton Formation (McBryde Member), Resource Management Services Palmyra tract, west of State Highway 263, Butler and Lowndes County, Alabama (UTM Zone 16, E 525,183 m, N 3,539,105 m, NAD83). Clayton Formation (Pine Barren Member), Shell Creek Park on Alabama River at State Highway 28 (Millers Ferry), north of Camden, Wilcox County, Alabama (UTM Zone 16, E 461,710 m,N3,553,196 m, NAD83).
Remarks.—Description is based on new material from Ala- bama. Although the type of Linthia prima is a steinkern (with a small amount silicified aboral test preserved), it is strongly characterized by the four genital pores, high anterior portion of the test, and pore patterning in the anterior ambulacrum. A number of schizasterid echinoid specimens agree closely in these details while differing significantly from other Linthia species in the collections. These are referred to L. prima, which is redescribed on the basis of this new material.
Genus Ova Gray, 1825 Ova rancoca new species
Figures 12.2, 12.3, 12.5, 12.6, 12.8, 12.9, 13.2
Types.—Holotype USNM 540894, paratypes USNM 488623, USNM 488773, and USNM 636365, from the Vincentown Formation, Vincentown, Burlington County, New Jersey.
Diagnosis.—Test oval, slightly cordiform; tallest behind apical disc. Apical disc nearly central, ethmolytic, two large genital pores. Anterior ambulacrum in deep, narrow sulcus, petals straight, in deep, narrow depressions, anterior petals longer than posterior. Peripetalous fasciole deeply indented; lateral fasciole
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branches from peripetalous fasciole after it bends inward from tip of petal to form a distinct offset.
Description.—Test oval, slightly cordiform; tallest behind apical disc, sloping towards anterior to a greater or lesser degree, posterior interambulacral plates form distinct ridge along meridional suture; oral surface slightly convex, with little or no keel. Apical disc nearly central, ethmolytic, two large genital pores, anterior genital plates imperforate. Anterior ambulacrum in deep, narrowsulcus, pore pairs unequal, outer pore largest, inner pores vestigial. Petals straight, in deep, narrow depressions, anterior petals two and a half times longer than posterior, anterior pair diverge at 120º, posterior pair at 55º–60º; pores elongate, conjugate, nearly equal in size; interporiferous zones narrower than poriferous zones. Periproct marginal, vertical, taller than wide. Peristome in anterior third of test, oval, wider than tall, no apparent lip. Labrum small and short, contacts sternal plates. Sternal plates large, about two-thirds of test length. Large phyllode pores surrounding peristome. Peripetalous fasciole deeply indented, parallels anterior petal for three quarters of its length, crosses above periproct near apex; lateral fasciole branches from peripetalous fasciole on interambulacral plate 5 after it bends inward from tip of petal to form a distinct offset (Fig. 13.2). Tubercles small aborally, larger along margin of anterior ambulacrum; larger and more scattered orally, with asymmetric areoles in paired interambulacra; posterior ambulacra naked orally.
Etymology.—Named for Rancocas Creek, source of much of the Vincentown material.
Occurrence.—Vincentown Formation, Rancocas Creek, Vincentown, Burlington County, New Jersey (UTM Zone 18, E 520,995m, N 4,421,446m, NAD83).
Remarks.—Superficially resembles Linthia alabamensis (Clark, 1915), but readily distinguished by two rather than four genital pores and the distinctive offset branching of the peripetalous and lateral fascioles (Fig. 13.2) as compared with L. alabamensis (Fig. 13.1). The posterior petals of O. rancoca n. sp. are proportionately shorter than those of L. alabamensis.
Discussion
Smith and Jeffery (2000) pointed out the need for careful taxonomic treatment based on informativemorphologic characters. In this study, revision of taxonomy as well as study of undescribed material has led to retention of several names synonymized by Smith and Jeffery (2000) and thus a higher degree of splitting of species than that employed by them. In particular, a distinction is made between European (and African) species and those of North America. It has long been noted (Gregory, 1892; Stefanini, 1924) that the fossil record of the early Cenozoic indicates significant
Figure 12. Linthia tumidula Clark, 1891 from the Vincentown Formation, New Jersey (exact locality unknown): (1) USNM 488624, aboral; (4) USNM 488624, profile. Ova rancoca n. sp. from the Vincentown Formation, Vincentown, Burlington County, NJ: (2) USNM 636365, paratype, aboral; (3) USNM 636365, paratype, detail of apical disc; (5) USNM 540894, holotype, aboral; (6) USNM 540894, holotype, oral; (8) USNM 540894, holotype, profile; (9) USNM 488623, paratype, posterior. Linthia prima (Cooke, 1942) from the Pine Barren Member, Clayton Formation: (7) MMNS 7095, aboral, Shell Creek Park, Wilcox County, AL; (10) MMNS 7096.1, aboral, Shell Creek Park, Wilcox County, AL; (11) MMNS 7095, posterior, Shell Creek Park, Wilcox County, AL; (12) MMNS 7095, profile, Shell Creek Park, Wilcox County, AL; (13) MMNS 7096.1, oral, Shell Creek Park, Wilcox County, AL; (14) MMNS 5301, aboral, McBryde Member, Clayton Formation, Palmyra Tract, Lowndes County, AL. Scale bars are (1, 2, 4–14) 20mm; (3) 2mm.
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