Hemiaster arcolensis Cooke, 1953
Plate: R2A
Series: Upper Cretaceous Group: Unknown Formation: Unknown
Locale: Unknown County: Red River, Texas
Length: 29.2 mm Width: 26.2 mm Height: 20.7 mm
Specimen in photo: U.S.N.M. 108397 Holotype
Paleobiology Depart. NMNH, Smithsonian Institution Red Ink
Specimen in photo from Alabama.
Plate: R2B
Series: Upper Cretaceous Group: Austin Chalk Formation: Atco
Locale: Austin County: Travis
Length: 29.2 mm Width: 26.2 mm Height: ? Crushed
Collector: Tyler Stoviah NPL ###### Non-vertebrate Paleo. Lab., Univ. of Tx.
Plate: R2C
Series: Upper Cretaceous Group: Austin Chalk Formation: Atco
Locale: Austin County: Travis
Length: 29.2 mm Width: 26.2 mm Height: ? Crushed
Collector: Tyler Stoviah NPL ###### Non-vertebrate Paleo. Lab., Univ. of Tx.
HOLOTYPE INFO:
Holotype: USNM 108397 (Cooke, 1953).
Locality: USGS 16290, 5 miles northeast of Aliceville, Pickens County, Alabama.
Stratigraphy: Arcola Limestone Member of the Mooreville Chalk.
Collector: [USGS Survey]
Repository: Paleobiology Dept., NMNH
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: Hemiasteridae H. L. Clark, 1917
Genus: HEMIASTER L. Agassiz, 1847
Species: Hemiaster arcolensis Cooke, 1953
TYPE SPECIES: Spatangus bufo Brongniart, 1822
DIAGNOSIS
A small to medium Hemiaster with a suboval outline, strongly convex above and weakly convex below. Distinguished by a central to slightly posterior apical system and small, widely spaced genital pores. The paired petals are wide and evenly concave; anterior pair is longer. The peripetalous fasciole is wide and conspicuous.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Austin; Taylor
Formations: Austin Chalk (Atco Formation); Ozan Formation (North Sulphur River area); Mooreville Chalk (Alabama).
Stratigraphic Units: Upper Cretaceous, Santonian to Early Campanian.
Counties: Travis, Fannin, Red River (Texas). Pickens (Alabama).
Abundance: Uncommon.
DESCRIPTION
TOP: Length, width, height: 29.2 mm L × 26.2 mm W × 20.7 mm H. Top shape: Suboval horizontal outline. Top domed: Strongly convex above; slightly higher behind than in front.
SIDE: Side shape: Slightly higher behind. Profile: Weakly truncated posterior end.
BOTTOM: Bottom shape: Weakly convex below. Sternum bordered by smooth ambulacral areas.
AMB: Amb shape: Anterior ambulacrum (III) is wide and evenly concave; very slightly depressed on the margin. Amb arrangement: Paired petals are straight, wide, and evenly concave. Anterior pair is longer than the posterior pair.
PORE PAIRS: Shape: Pores in paired petals are plainly elongated; poriferous zones are about as wide as the interporiferous zones. Unpaired Amb: Zygopores very narrow; pores separated by an erect, flattened bead.
TUBERCLES: Distribution: Small, perforated, set on small flake-like socles (bases). Condition: Not at all depressed.
GRANULES: [Not specified].
FASCIOLE: Peripetalous: Wide, conspicuous; very slightly incurved between the petals.
APICAL SYSTEM: Location: Slightly behind the center. Genital pores: Four pores; far apart. Plating: Madreporite small, central, and tumid.
PERIPROCT (ANUS): Shape: Small; slightly taller than wide. Location: Set high up on the weakly truncated posterior end.
PERISTOME (MOUTH): Location: At the anterior third. Lip: Bordered by a continuous raised rim; strongly labiate behind.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
ETYMOLOGY
Named for the Arcola Limestone member of the Mooreville Chalk, the type horizon in Alabama.
REMARKS & COMPARISONS
Remarks: This species has been historically misidentified in Texas collector literature (e.g., McKinzie et al., 2001) as Hemiaster beecheri. This identification is rejected for three reasons:
Plate: R2A
Series: Upper Cretaceous Group: Unknown Formation: Unknown
Locale: Unknown County: Red River, Texas
Length: 29.2 mm Width: 26.2 mm Height: 20.7 mm
Specimen in photo: U.S.N.M. 108397 Holotype
Paleobiology Depart. NMNH, Smithsonian Institution Red Ink
Specimen in photo from Alabama.
Plate: R2B
Series: Upper Cretaceous Group: Austin Chalk Formation: Atco
Locale: Austin County: Travis
Length: 29.2 mm Width: 26.2 mm Height: ? Crushed
Collector: Tyler Stoviah NPL ###### Non-vertebrate Paleo. Lab., Univ. of Tx.
Plate: R2C
Series: Upper Cretaceous Group: Austin Chalk Formation: Atco
Locale: Austin County: Travis
Length: 29.2 mm Width: 26.2 mm Height: ? Crushed
Collector: Tyler Stoviah NPL ###### Non-vertebrate Paleo. Lab., Univ. of Tx.
HOLOTYPE INFO:
Holotype: USNM 108397 (Cooke, 1953).
Locality: USGS 16290, 5 miles northeast of Aliceville, Pickens County, Alabama.
Stratigraphy: Arcola Limestone Member of the Mooreville Chalk.
Collector: [USGS Survey]
Repository: Paleobiology Dept., NMNH
SYNONYMY
- Hemiaster arcolensis Cooke, 1953
- Hemiaster beecheri (Clark) [Misidentification by McKinzie et al., 2001]
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: Hemiasteridae H. L. Clark, 1917
Genus: HEMIASTER L. Agassiz, 1847
Species: Hemiaster arcolensis Cooke, 1953
TYPE SPECIES: Spatangus bufo Brongniart, 1822
DIAGNOSIS
A small to medium Hemiaster with a suboval outline, strongly convex above and weakly convex below. Distinguished by a central to slightly posterior apical system and small, widely spaced genital pores. The paired petals are wide and evenly concave; anterior pair is longer. The peripetalous fasciole is wide and conspicuous.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Austin; Taylor
Formations: Austin Chalk (Atco Formation); Ozan Formation (North Sulphur River area); Mooreville Chalk (Alabama).
Stratigraphic Units: Upper Cretaceous, Santonian to Early Campanian.
Counties: Travis, Fannin, Red River (Texas). Pickens (Alabama).
Abundance: Uncommon.
DESCRIPTION
TOP: Length, width, height: 29.2 mm L × 26.2 mm W × 20.7 mm H. Top shape: Suboval horizontal outline. Top domed: Strongly convex above; slightly higher behind than in front.
SIDE: Side shape: Slightly higher behind. Profile: Weakly truncated posterior end.
BOTTOM: Bottom shape: Weakly convex below. Sternum bordered by smooth ambulacral areas.
AMB: Amb shape: Anterior ambulacrum (III) is wide and evenly concave; very slightly depressed on the margin. Amb arrangement: Paired petals are straight, wide, and evenly concave. Anterior pair is longer than the posterior pair.
PORE PAIRS: Shape: Pores in paired petals are plainly elongated; poriferous zones are about as wide as the interporiferous zones. Unpaired Amb: Zygopores very narrow; pores separated by an erect, flattened bead.
TUBERCLES: Distribution: Small, perforated, set on small flake-like socles (bases). Condition: Not at all depressed.
GRANULES: [Not specified].
FASCIOLE: Peripetalous: Wide, conspicuous; very slightly incurved between the petals.
APICAL SYSTEM: Location: Slightly behind the center. Genital pores: Four pores; far apart. Plating: Madreporite small, central, and tumid.
PERIPROCT (ANUS): Shape: Small; slightly taller than wide. Location: Set high up on the weakly truncated posterior end.
PERISTOME (MOUTH): Location: At the anterior third. Lip: Bordered by a continuous raised rim; strongly labiate behind.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
- Holotype USNM 108397: Alabama specimen (Cooke).
- Plate R2C & R2D: Crushed specimens from Austin, Travis County (Atco Fm). Collected by Benjamin Tyler Stoviak.
ETYMOLOGY
Named for the Arcola Limestone member of the Mooreville Chalk, the type horizon in Alabama.
REMARKS & COMPARISONS
Remarks: This species has been historically misidentified in Texas collector literature (e.g., McKinzie et al., 2001) as Hemiaster beecheri. This identification is rejected for three reasons:
- Biogeography: H. beecheri is a Western Interior Seaway species (South Dakota), whereas H. arcolensis is a Gulf Coast species (Alabama). The Texas faunas correlate strongly with the Mississippi Embayment.
- Stratigraphy: H. beecheri is Late Campanian (Virgin Creek Member), whereas H. arcolensis is Early Campanian/Santonian. The Texas occurrences (Ozan/Atco) align with the Early Campanian/Santonian range of arcolensis.
