Heteraster traski (Whitney, 1916)
Plate: HeTr-10
Series: Upper Cretaceous Group: Washita Formation: Buda
Locale: San Marcos County: Hays Stage: Cenomanian
Length: 25.4 mm Width: 23.7 mm Height: 16.3 mm
Specimen in photo: NPL 83015 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: TMM/NPL 17163 (Whitney Type Collection).
Locality: Shoal Creek, Austin, Travis County, Texas (Whitney, 1916).
Stratigraphy: Buda Limestone ("Base of upper division"), Washita 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: HETERASTER d'Orbigny, 1853
Species: Heteraster traski (Whitney, 1916)
TYPE SPECIES: Spatangus oblongus Brongniart, 1821
DIAGNOSIS
Test medium-sized, suboval, and anteriorly elevated; rises abruptly from the anterior margin. Unpaired ambulacrum pores consist of irregularly alternating elongate and rounded pairs. The left anterior genital plate narrows posteriorly and extends backward through the entire apical system (Whitney, 1916).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Buda Limestone
Stratigraphic Units: Upper Cretaceous, Cenomanian
Counties: Hays, Travis
DESCRIPTION
TOP: Length, width, height: 25.4 mm L × 23.7 mm W × 16.3 mm H.
Top shape: Suboval; widest part about midway of the length of the test (Whitney, 1916).
Top domed: Upper surface elevated; gently sloping toward the posterior (Whitney, 1916).
SIDE: Side shape: Rises abruptly from the anterior margin; highest point possibly in anterior. Posterior somewhat truncated (Whitney, 1916). Anterior slope is much steeper than in H. obliquatus.
BOTTOM: Bottom shape: Lower surface elevated in the region of the plastron (keel-like form); depressed about the peristome (Whitney, 1916).
AMB: Amb shape: Unpaired ambulacrum (III) situated in a broad anterior groove that forms a deep, wide notch in the anterior margin.
Amb arrangement: Anterior paired ambulacra flexuous. Posterior ambulacral areas much shorter than the others (Whitney, 1916).
PORE PAIRS: Arrangement: Unpaired ambulacrum (III) pores heterogeneous: alternating elongate and rounded pore pairs. Alternation is irregular (e.g., two elongate/one round, followed by five elongate/one round) (Whitney, 1916).
Paired ambs: Anterior paired ambs: anterior zone of rounded pores; posterior zone of round pores in internal row and elongate pores in external row. Five pairs of posterior zone correspond to about seven pairs of anterior zone. Posterior paired ambs: anterior row of round pores separated from posterior row of elongate pairs (Whitney, 1916).
TUBERCLES: Primary Areola shape: Broad areolas bordered by fine granules (Whitney, 1916).
Distribution: Surface of test covered with tubercles.
APICAL SYSTEM: Plating: Composed of four genital plates and five oculars. Right and left anterior genital plates are the largest. Distinctive feature: The left anterior plate narrows at its posterior end and extends backward throughout the entire apical system (Whitney, 1916).
Genital pores: Large perforations.
PERIPROCT (ANUS): Condition: Not preserved in the type specimens studied by Whitney.
PERISTOME (MOUTH): Shape: Transversely oval (Whitney, 1916).
Size: Small.
Location: Situated at the end of the first quarter of the length of the test.
Sunken: Depressed (Whitney, 1916).
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83015.
ETYMOLOGY
Likely named in honor of a local collector or geologist, possibly J.B. Trask, though Whitney (1916) does not specify.
REMARKS & COMPARISONS
Remarks: Cooke (1955) reviewed the holotype of Enallaster traski and suggested it appears to be a synonym of Heteraster bravoensis (Böse), noting that the irregular pore alternation is a variable trait. However, it is retained here as a distinct species based on Whitney's specific diagnosis of the apical system structure and anterior slope.
Comparisons:
Plate: HeTr-10
Series: Upper Cretaceous Group: Washita Formation: Buda
Locale: San Marcos County: Hays Stage: Cenomanian
Length: 25.4 mm Width: 23.7 mm Height: 16.3 mm
Specimen in photo: NPL 83015 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: TMM/NPL 17163 (Whitney Type Collection).
Locality: Shoal Creek, Austin, Travis County, Texas (Whitney, 1916).
Stratigraphy: Buda Limestone ("Base of upper division"), Washita Group.
SYNONYMY
- Enallaster traski Whitney, 1916
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: HETERASTER d'Orbigny, 1853
Species: Heteraster traski (Whitney, 1916)
TYPE SPECIES: Spatangus oblongus Brongniart, 1821
DIAGNOSIS
Test medium-sized, suboval, and anteriorly elevated; rises abruptly from the anterior margin. Unpaired ambulacrum pores consist of irregularly alternating elongate and rounded pairs. The left anterior genital plate narrows posteriorly and extends backward through the entire apical system (Whitney, 1916).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Buda Limestone
Stratigraphic Units: Upper Cretaceous, Cenomanian
Counties: Hays, Travis
DESCRIPTION
TOP: Length, width, height: 25.4 mm L × 23.7 mm W × 16.3 mm H.
Top shape: Suboval; widest part about midway of the length of the test (Whitney, 1916).
Top domed: Upper surface elevated; gently sloping toward the posterior (Whitney, 1916).
SIDE: Side shape: Rises abruptly from the anterior margin; highest point possibly in anterior. Posterior somewhat truncated (Whitney, 1916). Anterior slope is much steeper than in H. obliquatus.
BOTTOM: Bottom shape: Lower surface elevated in the region of the plastron (keel-like form); depressed about the peristome (Whitney, 1916).
AMB: Amb shape: Unpaired ambulacrum (III) situated in a broad anterior groove that forms a deep, wide notch in the anterior margin.
Amb arrangement: Anterior paired ambulacra flexuous. Posterior ambulacral areas much shorter than the others (Whitney, 1916).
PORE PAIRS: Arrangement: Unpaired ambulacrum (III) pores heterogeneous: alternating elongate and rounded pore pairs. Alternation is irregular (e.g., two elongate/one round, followed by five elongate/one round) (Whitney, 1916).
Paired ambs: Anterior paired ambs: anterior zone of rounded pores; posterior zone of round pores in internal row and elongate pores in external row. Five pairs of posterior zone correspond to about seven pairs of anterior zone. Posterior paired ambs: anterior row of round pores separated from posterior row of elongate pairs (Whitney, 1916).
TUBERCLES: Primary Areola shape: Broad areolas bordered by fine granules (Whitney, 1916).
Distribution: Surface of test covered with tubercles.
APICAL SYSTEM: Plating: Composed of four genital plates and five oculars. Right and left anterior genital plates are the largest. Distinctive feature: The left anterior plate narrows at its posterior end and extends backward throughout the entire apical system (Whitney, 1916).
Genital pores: Large perforations.
PERIPROCT (ANUS): Condition: Not preserved in the type specimens studied by Whitney.
PERISTOME (MOUTH): Shape: Transversely oval (Whitney, 1916).
Size: Small.
Location: Situated at the end of the first quarter of the length of the test.
Sunken: Depressed (Whitney, 1916).
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83015.
ETYMOLOGY
Likely named in honor of a local collector or geologist, possibly J.B. Trask, though Whitney (1916) does not specify.
REMARKS & COMPARISONS
Remarks: Cooke (1955) reviewed the holotype of Enallaster traski and suggested it appears to be a synonym of Heteraster bravoensis (Böse), noting that the irregular pore alternation is a variable trait. However, it is retained here as a distinct species based on Whitney's specific diagnosis of the apical system structure and anterior slope.
Comparisons:
- H. obliquatus: H. traski is more rounded in ambital outline, not as high, and has a much steeper anterior slope than H. obliquatus (Whitney, 1916).
- H. mexicanus: H. traski is more rounded and not as broad posteriorly as H. mexicanus (Whitney, 1916).
