Heteraster electus (Cragin, 1893)
Plate: HeEl-10
Series: Lower Cretaceous Group: Fredericksburg Formation: Walnut
Locale: Bee Cave County: Travis Stage: Albian
Length: 30.2 mm Width: 29.5 mm Height: 18.7 mm
Specimen in photo: NPL 83013 Hypotype
Collector: William R. Thompson, Jr.
University of Texas Non-vertebrate Paleo. Lab.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: Originally collected by Messrs. Taff and Drake (Cragin, 1893). Likely housed at the University of Texas (NPL) or Bureau of Economic Geology (BEG).
Locality: "No. 9 of their Sandy Creek section," Travis County, Texas (Cragin, 1893).
Stratigraphy: Trinity Division (Adkins, 1928); Walnut Formation.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
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 electus (Cragin, 1893)
TYPE SPECIES: Spatangus oblongus Brongniart, 1821
DIAGNOSIS
Test small, somewhat six-sided, broad, and anteriorly elevated; superior profile slopes rapidly backward from the apical disc. Unpaired ambulacral furrow is deep and ample. Posterior paired ambulacra are short and arcuated (Cragin, 1893).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg (Adkins, 1928); Trinity Division (Adkins, 1928).
Formations: Walnut Formation; originally described from the "Sandy Creek section" (Cragin, 1893).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Travis (Type Locality), Hays.
DESCRIPTION
TOP: Length, width, height: 30.2 mm L × 29.5 mm W × 18.7 mm H.
Top shape: Test cordate, angular (six-sided); widest part 55% from posterior. Posterior end truncated and nearly horizontal; anterior end curved. Rather broad (Cragin, 1893).
Top domed: Anteriorly elevated; superior part of the side-view outline slopes rapidly backward from a point a little in advance of the apical disc (Cragin, 1893). Highest point slightly posterior of center (approximately 40% from truncated end).
SIDE: Ambitus: About 40% from adoral surface.
Side shape: Very inflated with a partial box-like appearance. Disc-anal keel moderately prominent, obtuse (Cragin, 1893).
BOTTOM: Bottom shape: Rounded with keel.
AMB: Amb shape: Unpaired ambulacrum (III) situated in a deep sulcus; furrow is much deeper and ampler than the furrows of the paired ambulacra, about as large as in equal-sized specimens of Enallaster texanus (Cragin, 1893).
Amb arrangement: Anterior paired ambulacra flexuous, proximally curved then straight; approximately two times longer than posterior pair. Posterior paired ambulacra short, arcuated (about two-thirds as long as anterior pair), petaloid; petals open on outer ends (Cragin, 1893). Paired ambulacra moderately furrowed, less deeply than in E. hemiasterinus, but more deeply than in E. whitei (Cragin, 1893).
PORE PAIRS: Arrangement: Unpaired ambulacrum pores heterogeneous: a set of short elongated pores alternated with a set of long elongated pores (repeats).
Paired ambs: Anterior set of pore pairs in anterior paired ambulacra are small and round.
TUBERCLES: Primary Areola shape: Depressed.
Distribution: Tubercles more plentiful around unpaired ambulacrum and on the bottom surface.
APICAL SYSTEM: Location: Anterior of center (Cragin, 1893); located about 40% from truncated end.
Genital pores: Four gonopores.
PERIPROCT (ANUS): Shape & Size: Large, rounded (ovate), pointed above and rounded below (Cragin, 1893).
Location: High on truncated posterior end. Points downward in center.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Transversely oval; anterior margin presents a strong forward convexity, posterior margin straight or having a very slight posteriorly directed convexity (Cragin, 1893).
Size: Small.
Sunken: Depressed.
Plastron: Large and pronounced.
Visibility: Can clearly be seen from anterior end.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83013.
ETYMOLOGY
"Electus" is Latin for chosen or select.
REMARKS & COMPARISONS
Remarks: Miller (2009) states that H. electus, though untested, is probably a synonym of Heteraster texanus. Adkins (1928) listed this species under the Trinity Division.
Comparisons:
Plate: HeEl-10
Series: Lower Cretaceous Group: Fredericksburg Formation: Walnut
Locale: Bee Cave County: Travis Stage: Albian
Length: 30.2 mm Width: 29.5 mm Height: 18.7 mm
Specimen in photo: NPL 83013 Hypotype
Collector: William R. Thompson, Jr.
University of Texas Non-vertebrate Paleo. Lab.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: Originally collected by Messrs. Taff and Drake (Cragin, 1893). Likely housed at the University of Texas (NPL) or Bureau of Economic Geology (BEG).
Locality: "No. 9 of their Sandy Creek section," Travis County, Texas (Cragin, 1893).
Stratigraphy: Trinity Division (Adkins, 1928); Walnut Formation.
SYNONYMY
- Epiaster electus Cragin, 1893
- Enallaster electus (Cragin,1893) (Incorrect generic assignment in some later lists)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
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 electus (Cragin, 1893)
TYPE SPECIES: Spatangus oblongus Brongniart, 1821
DIAGNOSIS
Test small, somewhat six-sided, broad, and anteriorly elevated; superior profile slopes rapidly backward from the apical disc. Unpaired ambulacral furrow is deep and ample. Posterior paired ambulacra are short and arcuated (Cragin, 1893).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg (Adkins, 1928); Trinity Division (Adkins, 1928).
Formations: Walnut Formation; originally described from the "Sandy Creek section" (Cragin, 1893).
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Travis (Type Locality), Hays.
DESCRIPTION
TOP: Length, width, height: 30.2 mm L × 29.5 mm W × 18.7 mm H.
Top shape: Test cordate, angular (six-sided); widest part 55% from posterior. Posterior end truncated and nearly horizontal; anterior end curved. Rather broad (Cragin, 1893).
Top domed: Anteriorly elevated; superior part of the side-view outline slopes rapidly backward from a point a little in advance of the apical disc (Cragin, 1893). Highest point slightly posterior of center (approximately 40% from truncated end).
SIDE: Ambitus: About 40% from adoral surface.
Side shape: Very inflated with a partial box-like appearance. Disc-anal keel moderately prominent, obtuse (Cragin, 1893).
BOTTOM: Bottom shape: Rounded with keel.
AMB: Amb shape: Unpaired ambulacrum (III) situated in a deep sulcus; furrow is much deeper and ampler than the furrows of the paired ambulacra, about as large as in equal-sized specimens of Enallaster texanus (Cragin, 1893).
Amb arrangement: Anterior paired ambulacra flexuous, proximally curved then straight; approximately two times longer than posterior pair. Posterior paired ambulacra short, arcuated (about two-thirds as long as anterior pair), petaloid; petals open on outer ends (Cragin, 1893). Paired ambulacra moderately furrowed, less deeply than in E. hemiasterinus, but more deeply than in E. whitei (Cragin, 1893).
PORE PAIRS: Arrangement: Unpaired ambulacrum pores heterogeneous: a set of short elongated pores alternated with a set of long elongated pores (repeats).
Paired ambs: Anterior set of pore pairs in anterior paired ambulacra are small and round.
TUBERCLES: Primary Areola shape: Depressed.
Distribution: Tubercles more plentiful around unpaired ambulacrum and on the bottom surface.
APICAL SYSTEM: Location: Anterior of center (Cragin, 1893); located about 40% from truncated end.
Genital pores: Four gonopores.
PERIPROCT (ANUS): Shape & Size: Large, rounded (ovate), pointed above and rounded below (Cragin, 1893).
Location: High on truncated posterior end. Points downward in center.
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Transversely oval; anterior margin presents a strong forward convexity, posterior margin straight or having a very slight posteriorly directed convexity (Cragin, 1893).
Size: Small.
Sunken: Depressed.
Plastron: Large and pronounced.
Visibility: Can clearly be seen from anterior end.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83013.
ETYMOLOGY
"Electus" is Latin for chosen or select.
REMARKS & COMPARISONS
Remarks: Miller (2009) states that H. electus, though untested, is probably a synonym of Heteraster texanus. Adkins (1928) listed this species under the Trinity Division.
Comparisons:
- H. whitei: Cragin (1893) notes the test of H. electus is posteriorly much broader than that of H. whitei, and the paired ambulacra are more deeply furrowed.
- H. texanus: The unpaired ambulacral furrow is about as large as in equal-sized specimens of H. texanus (Cragin, 1893).
