Pliotoxaster whitei (Clark 1891)
Plate: PlWi-10
Series: Lower Cretaceous Group: Fredericksburg Formation: Goodland
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 29.9 mm Width: 28.1 mm Height: 18.0 mm
Specimen in photo: NPL 83034 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 103233 (Originally Johns Hopkins Collection) (Clark, 1891).
Locality: West of Fort Worth, Tarrant County, Texas (Clark, 1891).
Stratigraphy: Goodland Limestone, Fredericksburg Group.
SYNONYMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Toxasteridae Lambert, 1920
Genus: PLIOTOXASTER Fourtau, 1907
Species: Pliotoxaster whitei (Clark, 1891)
TYPE SPECIES: Spatangus collegnii Sismonda, 1844
DIAGNOSIS
Test small, cordiform, and convex. Ambulacra are moderately broad and petaloidal; the anterolateral pair is bent slightly backward. Distinguished from P. comanchei by being smaller, less elevated, and having shallower ambulacral furrows (Clark, 1915; Cooke, 1955).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg (Primary); Washita (Lower) (Clark & Twitchell, 1915).
Formations: Goodland Limestone; Comanche Peak Limestone; Walnut Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant, Travis, Williamson.
Abundance: Common in the Fredericksburg Group.
DESCRIPTION
TOP: Length, width, height: 29.9 mm L × 28.1 mm W × 18.0 mm H. Top shape: Cordiform (Clark & Twitchell, 1915). Top domed: Upper surface distinctly elevated, but less so than in P. comanchei. The apex occupies a point anterior to the center (Clark & Twitchell, 1915).
SIDE: Side shape: Sides inflated with a well-marked groove at the center of the anterior face (Clark & Twitchell, 1915). Profile: Prominent truncated surface on the posterior margin.
BOTTOM: Bottom shape: Lower surface flat with the exception of the peristomal depression (Clark & Twitchell, 1915).
AMB: Amb shape: Moderately broad; subpetaloidal in their upper part, but this feature does not continue to the margin (Clark & Twitchell, 1915). Amb arrangement: Anterolateral pair bent slightly backward in their upper part and are distinctly larger than the posterolaterals (Clark & Twitchell, 1915).
PORE PAIRS: Shape: Pores in paired ambulacra have elongated openings (Clark & Twitchell, 1915). Arrangement: Pores in the unpaired ambulacrum are smaller and nearer together (Clark & Twitchell, 1915).
TUBERCLES: Distribution: Surface of plates covered with minute tubercles (Clark & Twitchell, 1915).
GRANULES: Distribution: Microscopic granules intervene between tubercles (Clark & Twitchell, 1915).
FASCIOLE: Peripetalous: Clark (1915) describes an "indistinct" peripetalous fasciole. However, Cooke (1955) assigns this to Pliotoxaster specifically because fascioles are absent or not preserved in the type material, distinguishing it from Hemiaster.
APICAL SYSTEM: Location: Subcentral (Clark & Twitchell, 1915). Size: Small and compact. Plating: Consists of four large perforated genital plates and five oculars (Clark & Twitchell, 1915).
PERIPROCT (ANUS): Shape: Small and oval. Location: Situated high on the truncated posterior margin (Clark & Twitchell, 1915).
PERISTOME (MOUTH): Shape: Transversely subpentagonal to oval. Location: Situated near the anterior margin (Clark & Twitchell, 1915).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83034. Collected by William R. Thompson, Jr.
ETYMOLOGY
Named in honor of Dr. Charles A. White (1826–1910), paleontologist with the U.S. Geological Survey (Clark, 1891).
REMARKS & COMPARISONS
Remarks: Clark (1915) originally placed this in Hemiaster. Cooke (1955) transferred it to Pliotoxaster based on the absence of a fasciole. Cragin (1893) described Epiaster hemiasterinus from the Grayson Formation, which Clark (1915) and Adkins (1928) later synonymized with H. whitei, though Cragin noted his species had deeper ambulacral grooves.
Comparisons:
Plate: PlWi-10
Series: Lower Cretaceous Group: Fredericksburg Formation: Goodland
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 29.9 mm Width: 28.1 mm Height: 18.0 mm
Specimen in photo: NPL 83034 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 103233 (Originally Johns Hopkins Collection) (Clark, 1891).
Locality: West of Fort Worth, Tarrant County, Texas (Clark, 1891).
Stratigraphy: Goodland Limestone, Fredericksburg Group.
SYNONYMY
- Hemiaster whitei Clark, 1891
- Epiaster hemiasterinus Cragin, 1893 (fide Adkins, 1928)
- Pliotoxaster whitei (Clark) Cooke, 1955
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Toxasteridae Lambert, 1920
Genus: PLIOTOXASTER Fourtau, 1907
Species: Pliotoxaster whitei (Clark, 1891)
TYPE SPECIES: Spatangus collegnii Sismonda, 1844
DIAGNOSIS
Test small, cordiform, and convex. Ambulacra are moderately broad and petaloidal; the anterolateral pair is bent slightly backward. Distinguished from P. comanchei by being smaller, less elevated, and having shallower ambulacral furrows (Clark, 1915; Cooke, 1955).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg (Primary); Washita (Lower) (Clark & Twitchell, 1915).
Formations: Goodland Limestone; Comanche Peak Limestone; Walnut Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant, Travis, Williamson.
Abundance: Common in the Fredericksburg Group.
DESCRIPTION
TOP: Length, width, height: 29.9 mm L × 28.1 mm W × 18.0 mm H. Top shape: Cordiform (Clark & Twitchell, 1915). Top domed: Upper surface distinctly elevated, but less so than in P. comanchei. The apex occupies a point anterior to the center (Clark & Twitchell, 1915).
SIDE: Side shape: Sides inflated with a well-marked groove at the center of the anterior face (Clark & Twitchell, 1915). Profile: Prominent truncated surface on the posterior margin.
BOTTOM: Bottom shape: Lower surface flat with the exception of the peristomal depression (Clark & Twitchell, 1915).
AMB: Amb shape: Moderately broad; subpetaloidal in their upper part, but this feature does not continue to the margin (Clark & Twitchell, 1915). Amb arrangement: Anterolateral pair bent slightly backward in their upper part and are distinctly larger than the posterolaterals (Clark & Twitchell, 1915).
PORE PAIRS: Shape: Pores in paired ambulacra have elongated openings (Clark & Twitchell, 1915). Arrangement: Pores in the unpaired ambulacrum are smaller and nearer together (Clark & Twitchell, 1915).
TUBERCLES: Distribution: Surface of plates covered with minute tubercles (Clark & Twitchell, 1915).
GRANULES: Distribution: Microscopic granules intervene between tubercles (Clark & Twitchell, 1915).
FASCIOLE: Peripetalous: Clark (1915) describes an "indistinct" peripetalous fasciole. However, Cooke (1955) assigns this to Pliotoxaster specifically because fascioles are absent or not preserved in the type material, distinguishing it from Hemiaster.
APICAL SYSTEM: Location: Subcentral (Clark & Twitchell, 1915). Size: Small and compact. Plating: Consists of four large perforated genital plates and five oculars (Clark & Twitchell, 1915).
PERIPROCT (ANUS): Shape: Small and oval. Location: Situated high on the truncated posterior margin (Clark & Twitchell, 1915).
PERISTOME (MOUTH): Shape: Transversely subpentagonal to oval. Location: Situated near the anterior margin (Clark & Twitchell, 1915).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83034. Collected by William R. Thompson, Jr.
ETYMOLOGY
Named in honor of Dr. Charles A. White (1826–1910), paleontologist with the U.S. Geological Survey (Clark, 1891).
REMARKS & COMPARISONS
Remarks: Clark (1915) originally placed this in Hemiaster. Cooke (1955) transferred it to Pliotoxaster based on the absence of a fasciole. Cragin (1893) described Epiaster hemiasterinus from the Grayson Formation, which Clark (1915) and Adkins (1928) later synonymized with H. whitei, though Cragin noted his species had deeper ambulacral grooves.
Comparisons:
- Pliotoxaster comanchei: P. whitei is distinguished by being much smaller, less elevated, and having shallower ambulacral furrows than P. comanchei (Ikins, 1940).
- Macraster elegans: Clark (1915) noted a close association with H. elegans (now Macraster), but P. whitei is more elevated, has shorter ambulacral furrows, and a differently situated periproct.
