Pliotoxaster comanchei (Clark, 1915)
Plate: PlCo-10
Series: Lower Cretaceous Group: Trinity Formation: Glen rose
Locale: Hunter County: Comal Stage: Albian
Length: 45.0 mm Width: 40.3 mm Height: 30.3 mm
Collection: Bill Thompson
Repository: Private Collection
HOLOTYPE INFO:
Holotype: USNM 19130 (Clark, 1915).
Locality: Austin, Travis County, Texas (Clark, 1915).
Stratigraphy: Glen Rose Formation (Lower Member).
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 comanchei (Clark, 1915)
TYPE SPECIES: Spatangus collegnii Sismonda, 1844
DIAGNOSIS
Test small to medium, cordiform, and high; sides inflated and lower surface flat. Apex positioned forward of the center. Ambulacra are rather narrow and depressed; posterolateral petals are considerably shorter than the anterolateral. Periproct is visible from above (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Glen Rose Formation (Lower Member, Unit 2; "Salenia bed", and Upper)
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Bandera, Comal, Kendall, Travis, Bexar
Abundance: Common in specific zones of the Lower Glen Rose.
DESCRIPTION
TOP: Length, width, height: 45.0 mm L × 40.3 mm W × 30.3 mm H. Top shape: Cordiform in ambital outline (Clark & Twitchell, 1915). Top domed: Upper surface somewhat inflated. Apex is forward of the center.
SIDE: Ambitus: Sides are inflated. Side shape: High profile. Posterior surface slopes.
BOTTOM: Bottom shape: Lower surface nearly flat (Clark & Twitchell, 1915).
AMB: Amb shape: Rather narrow and depressed. Unpaired anterior ambulacrum lies in a broad, moderately depressed sulcus. Amb arrangement: Poriferous zones are petaloidal but narrow. Posterolateral pair is considerably shorter than the anterolateral pair (Clark & Twitchell, 1915).
PORE PAIRS: Not detailed
TUBERCLES: Distribution: Implied by "irregularly scattered granules".
GRANULES: Distribution: Interambulacra covered with numerous irregularly scattered granules. Granules also scattered over the fasciole surface (Clark & Twitchell, 1915).
FASCIOLE: Peripetalous: Described by Clark (1915) as "broad and distinct" and clearly marked. (Note: Placement in Pliotoxaster by Cooke usually implies fascioles are absent or diffuse; Clark's original description contrasts with this later generic assignment).
APICAL SYSTEM: Location: Nearly central on the upper surface (Clark & Twitchell, 1915).
PERIPROCT (ANUS): Shape: Small. Location: High on the sloping posterior surface. Visibility: Showing clearly from above (Clark & Twitchell, 1915).
PERISTOME (MOUTH): Shape: Transversely ovate. Location: Near the forward margin (Clark & Twitchell, 1915).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen from the Collection of Bill Thompson.
ETYMOLOGY
Named for the Comanche Series, the major Lower Cretaceous division of Texas.
REMARKS & COMPARISONS
Remarks: Clark (1915) regarded H. comanchei as the earliest of the Comanchean Hemiasters and a potential ancestral form for H. whitei, H. elegans, and H. calvini. This species is stratigraphically restricted to the Lower Glen Rose (Unit 2).
Clark's description mentions a "distinct" fasciole (which is usually a trait of Hemiaster)
Comparisons:
Ikins (1940) emphasized the "excessive height" of this species as a key character. While Adkins (1930) reported this species as abundant in the Walnut/Comanche Peak formations of Bell County, those specimens are now recognized as a distinct new species (P. donaldtrumpi Thompson, 2020), restricting P. comanchei primarily to the Trinity Group (Glen Rose).
Plate: PlCo-10
Series: Lower Cretaceous Group: Trinity Formation: Glen rose
Locale: Hunter County: Comal Stage: Albian
Length: 45.0 mm Width: 40.3 mm Height: 30.3 mm
Collection: Bill Thompson
Repository: Private Collection
HOLOTYPE INFO:
Holotype: USNM 19130 (Clark, 1915).
Locality: Austin, Travis County, Texas (Clark, 1915).
Stratigraphy: Glen Rose Formation (Lower Member).
SYNONYMY
- Hemiaster comanchei Clark, 1915
- Palhemiaster comanchei (Clark) Lambert, 1920
- Pliotoxaster comanchei (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 comanchei (Clark, 1915)
TYPE SPECIES: Spatangus collegnii Sismonda, 1844
DIAGNOSIS
Test small to medium, cordiform, and high; sides inflated and lower surface flat. Apex positioned forward of the center. Ambulacra are rather narrow and depressed; posterolateral petals are considerably shorter than the anterolateral. Periproct is visible from above (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Glen Rose Formation (Lower Member, Unit 2; "Salenia bed", and Upper)
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Bandera, Comal, Kendall, Travis, Bexar
Abundance: Common in specific zones of the Lower Glen Rose.
DESCRIPTION
TOP: Length, width, height: 45.0 mm L × 40.3 mm W × 30.3 mm H. Top shape: Cordiform in ambital outline (Clark & Twitchell, 1915). Top domed: Upper surface somewhat inflated. Apex is forward of the center.
SIDE: Ambitus: Sides are inflated. Side shape: High profile. Posterior surface slopes.
BOTTOM: Bottom shape: Lower surface nearly flat (Clark & Twitchell, 1915).
AMB: Amb shape: Rather narrow and depressed. Unpaired anterior ambulacrum lies in a broad, moderately depressed sulcus. Amb arrangement: Poriferous zones are petaloidal but narrow. Posterolateral pair is considerably shorter than the anterolateral pair (Clark & Twitchell, 1915).
PORE PAIRS: Not detailed
TUBERCLES: Distribution: Implied by "irregularly scattered granules".
GRANULES: Distribution: Interambulacra covered with numerous irregularly scattered granules. Granules also scattered over the fasciole surface (Clark & Twitchell, 1915).
FASCIOLE: Peripetalous: Described by Clark (1915) as "broad and distinct" and clearly marked. (Note: Placement in Pliotoxaster by Cooke usually implies fascioles are absent or diffuse; Clark's original description contrasts with this later generic assignment).
APICAL SYSTEM: Location: Nearly central on the upper surface (Clark & Twitchell, 1915).
PERIPROCT (ANUS): Shape: Small. Location: High on the sloping posterior surface. Visibility: Showing clearly from above (Clark & Twitchell, 1915).
PERISTOME (MOUTH): Shape: Transversely ovate. Location: Near the forward margin (Clark & Twitchell, 1915).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen from the Collection of Bill Thompson.
ETYMOLOGY
Named for the Comanche Series, the major Lower Cretaceous division of Texas.
REMARKS & COMPARISONS
Remarks: Clark (1915) regarded H. comanchei as the earliest of the Comanchean Hemiasters and a potential ancestral form for H. whitei, H. elegans, and H. calvini. This species is stratigraphically restricted to the Lower Glen Rose (Unit 2).
Clark's description mentions a "distinct" fasciole (which is usually a trait of Hemiaster)
Comparisons:
- Pliotoxaster whitei: P. comanchei is distinguished by its greater height and more sloping sides compared to the lower P. whitei.
Ikins (1940) emphasized the "excessive height" of this species as a key character. While Adkins (1930) reported this species as abundant in the Walnut/Comanche Peak formations of Bell County, those specimens are now recognized as a distinct new species (P. donaldtrumpi Thompson, 2020), restricting P. comanchei primarily to the Trinity Group (Glen Rose).
