Hemiaster benhurensis Stephenson, 1941
Plate: HeBen-10
Series: Upper Cretaceous Group: Lower Navarro Formation: Neylandville Marl
Locale: Ben Hur County: Limestone Stage: Early Maastrichtian
Length: 20.0 mm Width: 19.5 mm Height: 14.7 mm
Specimen in photo: U.S.N.M. 76282 Holotype
Paleobiology Depart. NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 76282 — National Museum of Natural History, Smithsonian Institution (Stephenson, 1941)
Locality: 2.5 miles east-northeast of Ben Hur, Limestone County, Texas (Stephenson, 1941)
Stratigraphy: Neylandville Marl (Stephenson, 1941)
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 L. Clark, 1917
Genus: HEMIASTER L. Agassiz, 1847
Species: Hemiaster benhurensis Stephenson, 1941
TYPE SPECIES: Spatangus bufo Brongniart, 1822
DIAGNOSIS
Small, high, subcordate test with deep anterior sulcus. Anterior paired petals about twice as long as posterior paired petals. Periproct vertically oval, situated high on a vertically truncated posterior (Stephenson, 1941).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Navarro
Formations: Neylandville Marl
Stratigraphic Units: Upper Cretaceous, Maastrichtian
Counties: Limestone County
DESCRIPTION
TOP: Length, width, height: 20.0 mm L × 19.5 mm W × 14.7 mm H
Top shape: Small, round, with an angular appearance; anterior sulcus where unpaired amb cuts margin; slight point at posterior end.
Flatness: Upper surface nearly flat from side profile.
SIDE: Ambitus: 50% from base.
Side shape: Sides inflated; posterior end highly truncated.
Apex: Located 25% from posterior end.
BOTTOM: Bottom shape: Rounded.
AMB: Amb shape: Paired ambs petaloid. Unpaired amb is the longest, flat between either sides of pore pairs.
Amb arrangement: Anterior ambs twice as long as posterior ambs.
Amb primary zones: Petals closed on posterior ambs.
PORE PAIRS: Shape: Round in unpaired amb; round in paired ambs.
Arrangement: In paired ambs, pore pairs quite separated and oblique.
TUBERCLES: Primary tubercles: Small. Larger on bottom.
Primary Areola shape: Sunken.
FASCIOLE: Peripetalous fasciole visible.
APICAL SYSTEM: Condition: Unclear since specimen damaged.
PERIPROCT (ANUS): Shape & Size: Vertically oval; narrow; slightly pointed aborally.
Location: High on truncated end; about 60% from bottom.
PERISTOME (MOUTH): Size: Small.
Location: Located half way between anterior end and center point
Sunken: Slightly depressed.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 76282; specimen damaged (apical area).
ETYMOLOGY
Named for the town of Ben Hur, Texas, near the type locality (Stephenson, 1941).
REMARKS & COMPARISONS
Remarks: Stephenson (1941) noted that this species is distinguished by its small size, high test, and specific inequality of the paired petals.
Comparisons: Stephenson (1941) compared H. benhurensis to Hemiaster wetherbyi de Loriol, stating it is relatively higher, more inflated, and has a flatter base than wetherbyi.
Plate: HeBen-10
Series: Upper Cretaceous Group: Lower Navarro Formation: Neylandville Marl
Locale: Ben Hur County: Limestone Stage: Early Maastrichtian
Length: 20.0 mm Width: 19.5 mm Height: 14.7 mm
Specimen in photo: U.S.N.M. 76282 Holotype
Paleobiology Depart. NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 76282 — National Museum of Natural History, Smithsonian Institution (Stephenson, 1941)
Locality: 2.5 miles east-northeast of Ben Hur, Limestone County, Texas (Stephenson, 1941)
Stratigraphy: Neylandville Marl (Stephenson, 1941)
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 L. Clark, 1917
Genus: HEMIASTER L. Agassiz, 1847
Species: Hemiaster benhurensis Stephenson, 1941
TYPE SPECIES: Spatangus bufo Brongniart, 1822
DIAGNOSIS
Small, high, subcordate test with deep anterior sulcus. Anterior paired petals about twice as long as posterior paired petals. Periproct vertically oval, situated high on a vertically truncated posterior (Stephenson, 1941).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Navarro
Formations: Neylandville Marl
Stratigraphic Units: Upper Cretaceous, Maastrichtian
Counties: Limestone County
DESCRIPTION
TOP: Length, width, height: 20.0 mm L × 19.5 mm W × 14.7 mm H
Top shape: Small, round, with an angular appearance; anterior sulcus where unpaired amb cuts margin; slight point at posterior end.
Flatness: Upper surface nearly flat from side profile.
SIDE: Ambitus: 50% from base.
Side shape: Sides inflated; posterior end highly truncated.
Apex: Located 25% from posterior end.
BOTTOM: Bottom shape: Rounded.
AMB: Amb shape: Paired ambs petaloid. Unpaired amb is the longest, flat between either sides of pore pairs.
Amb arrangement: Anterior ambs twice as long as posterior ambs.
Amb primary zones: Petals closed on posterior ambs.
PORE PAIRS: Shape: Round in unpaired amb; round in paired ambs.
Arrangement: In paired ambs, pore pairs quite separated and oblique.
TUBERCLES: Primary tubercles: Small. Larger on bottom.
Primary Areola shape: Sunken.
FASCIOLE: Peripetalous fasciole visible.
APICAL SYSTEM: Condition: Unclear since specimen damaged.
PERIPROCT (ANUS): Shape & Size: Vertically oval; narrow; slightly pointed aborally.
Location: High on truncated end; about 60% from bottom.
PERISTOME (MOUTH): Size: Small.
Location: Located half way between anterior end and center point
Sunken: Slightly depressed.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 76282; specimen damaged (apical area).
ETYMOLOGY
Named for the town of Ben Hur, Texas, near the type locality (Stephenson, 1941).
REMARKS & COMPARISONS
Remarks: Stephenson (1941) noted that this species is distinguished by its small size, high test, and specific inequality of the paired petals.
Comparisons: Stephenson (1941) compared H. benhurensis to Hemiaster wetherbyi de Loriol, stating it is relatively higher, more inflated, and has a flatter base than wetherbyi.
