Protoscutella tuomeyi (Twitchell, 1915)
Plate: PrTu-10
Series: Eocene Group: Claiborne Formation: Weches
Locale: San Augustine County: San Augustine Stage: Lutetian
Length: 12.9 mm Width: 13.1 mm Height: 3.1 mm
Specimen in photo: NPL 83038 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 137656 (Twitchell, 1915; Cooke, 1959).
Locality: North Santee River, Georgetown County, South Carolina.
Stratigraphy: McBean Formation (Claiborne Group).
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Clypeasteroida A. Agassiz, 1872
Family: Protoscutellidae Durham, 1955
Genus: PROTOSCUTELLA Stefanini, 1924
Species: Protoscutella tuomeyi (Twitchell, 1915)
TYPE SPECIES: Scutella mississippiensis Twitchell, 1915
DIAGNOSIS
Test subovate, pointed anteriorly, and truncated posteriorly. Greatly depressed with a flat marginal area and slightly tumid center. Periproct is inframarginal, situated about one-fourth the distance from the posterior margin to the peristome. Distinguished from Periarchus by the closer proximity of the periproct to the margin (Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Claiborne
Formations: Weches Formation (Texas); McBean Formation (South Carolina).
Stratigraphic Units: Paleogene, Middle Eocene.
Counties: San Augustine (Texas).
Abundance: Common in Texas. Type was unique at time of description.
DESCRIPTION
TOP: Length, width, height: 12.9 mm L × 13.1 mm W × 3.1 mm H. Top shape: Subovate; broadest posteriorly, narrowing until somewhat pointed anteriorly. Truncated along the middle of the posterior border (Twitchell, 1915). Top domed: Greatly depressed; rises only slightly within the petaloid area to form a very low, broad mound.
SIDE: Side shape: Margin thin with two shallow notches opposite the ends of the posterior petals.
BOTTOM: Bottom shape: Flat or slightly concave from edge to edge.
AMB: Amb shape: Petals are narrowly elliptical and subequal in length. Amb arrangement: Posterior pair extends about half way to the margin; others extend decidedly more than half way.
PORE PAIRS: Shape: Inner row oval, outer row slit-like. Arrangement: Conjugate. Poriferous zones are rather wide, almost as wide as interporiferous areas.
TUBERCLES: Distribution: Surface covered with small uniform tubercles, slightly larger on the underside.
GRANULES: See Tubercles.
FASCIOLE: Absent.
APICAL SYSTEM: Location: Central or subcentral. Plating: Madreporite relatively large and flush. Genital pores: 5 pores near the edge.
PERIPROCT (ANUS): Shape: Very small and subcircular. Location: Inframarginal (on the oral surface); situated about one-fourth the distance from the posterior margin to the peristome.
PERISTOME (MOUTH): Shape: Circular or subcircular. Size: Small. Location: Central or subcentral.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83038. Collected by William R. Thompson, Jr. Note: This specimen is significantly smaller than typical adult scutellids, potentially representing a juvenile.
ETYMOLOGY
Named in honor of Michael Tuomey (1805–1857), distinguished geologist and paleontologist of South Carolina and Alabama.
REMARKS & COMPARISONS
Remarks: This species was transferred to Protoscutella by Stefanini (1924). It is stratigraphically associated with the Middle Eocene Protoscutella mississippiensis.
Comparisons:
Plate: PrTu-10
Series: Eocene Group: Claiborne Formation: Weches
Locale: San Augustine County: San Augustine Stage: Lutetian
Length: 12.9 mm Width: 13.1 mm Height: 3.1 mm
Specimen in photo: NPL 83038 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 137656 (Twitchell, 1915; Cooke, 1959).
Locality: North Santee River, Georgetown County, South Carolina.
Stratigraphy: McBean Formation (Claiborne Group).
SYNONYMY
- Scutella tuomeyi Twitchell, 1915
- Protoscutella tuomeyi (Twitchell) Stefanini, 1924
- Periarchus lyelli (Conrad) (misidentified in some collections)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Clypeasteroida A. Agassiz, 1872
Family: Protoscutellidae Durham, 1955
Genus: PROTOSCUTELLA Stefanini, 1924
Species: Protoscutella tuomeyi (Twitchell, 1915)
TYPE SPECIES: Scutella mississippiensis Twitchell, 1915
DIAGNOSIS
Test subovate, pointed anteriorly, and truncated posteriorly. Greatly depressed with a flat marginal area and slightly tumid center. Periproct is inframarginal, situated about one-fourth the distance from the posterior margin to the peristome. Distinguished from Periarchus by the closer proximity of the periproct to the margin (Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Claiborne
Formations: Weches Formation (Texas); McBean Formation (South Carolina).
Stratigraphic Units: Paleogene, Middle Eocene.
Counties: San Augustine (Texas).
Abundance: Common in Texas. Type was unique at time of description.
DESCRIPTION
TOP: Length, width, height: 12.9 mm L × 13.1 mm W × 3.1 mm H. Top shape: Subovate; broadest posteriorly, narrowing until somewhat pointed anteriorly. Truncated along the middle of the posterior border (Twitchell, 1915). Top domed: Greatly depressed; rises only slightly within the petaloid area to form a very low, broad mound.
SIDE: Side shape: Margin thin with two shallow notches opposite the ends of the posterior petals.
BOTTOM: Bottom shape: Flat or slightly concave from edge to edge.
AMB: Amb shape: Petals are narrowly elliptical and subequal in length. Amb arrangement: Posterior pair extends about half way to the margin; others extend decidedly more than half way.
PORE PAIRS: Shape: Inner row oval, outer row slit-like. Arrangement: Conjugate. Poriferous zones are rather wide, almost as wide as interporiferous areas.
TUBERCLES: Distribution: Surface covered with small uniform tubercles, slightly larger on the underside.
GRANULES: See Tubercles.
FASCIOLE: Absent.
APICAL SYSTEM: Location: Central or subcentral. Plating: Madreporite relatively large and flush. Genital pores: 5 pores near the edge.
PERIPROCT (ANUS): Shape: Very small and subcircular. Location: Inframarginal (on the oral surface); situated about one-fourth the distance from the posterior margin to the peristome.
PERISTOME (MOUTH): Shape: Circular or subcircular. Size: Small. Location: Central or subcentral.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83038. Collected by William R. Thompson, Jr. Note: This specimen is significantly smaller than typical adult scutellids, potentially representing a juvenile.
ETYMOLOGY
Named in honor of Michael Tuomey (1805–1857), distinguished geologist and paleontologist of South Carolina and Alabama.
REMARKS & COMPARISONS
Remarks: This species was transferred to Protoscutella by Stefanini (1924). It is stratigraphically associated with the Middle Eocene Protoscutella mississippiensis.
Comparisons:
- Periarchus lyelli: P. tuomeyi is more pointed anteriorly, truncated posteriorly, and has the periproct located much nearer to the posterior border than P. lyelli.
- Protoscutella mississippiensis: P. tuomeyi resembles P. mississippiensis in general appearance but is distinguished by the inframarginal position of its periproct (vs. marginal/submarginal in mississippiensis) (Twitchell, 1915).
- Protoscutella conradi: P. tuomeyi resembles P. conradi but is separated by the lack of a subquadrate posterior end and the specific periproct position (Twitchell, 1915). Cooke (1959) suggested tuomeyi might be a variant of conradi.
