Heteraster brewsterensis Thompson, 2020
Plate: HeBr-10
Series: Upper Cretaceous Group: Washita Formation: Del Rio
Locale: Buck Hill County: Brewster Stage: Cenomanian
Length: 35.6 mm Width: 33.7 mm Height: 29.2 mm
Specimen in photo: NPL 94332 Holotype
Collector: Dr. Steven Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94332
Paratypes: NPL 94333
Locality: Buck Hill, Brewster County, Texas
Stratigraphy: Del Rio Formation, Washita Group
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 brewsterensis Thompson, 2020
TYPE SPECIES: Spatangus oblongus Brongniart, 1821
DIAGNOSIS
An inflated Heteraster from the Del Rio Formation of Brewster County, Texas. Unlike any Heteraster of Texas, distinguished by an ambitus that slopes the entire length of the test (oblique ambitus).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Del Rio Formation
Stratigraphic Units: Upper Cretaceous, Cenomanian
Counties: Brewster
DESCRIPTION
TOP: Length, width, height: 35.6 mm L × 33.7 mm W × 29.2 mm H.
Top shape: Cordate (heart-shaped); greatest width anterior of center.
Top domed: Deep sulcus on anterior end; flat at posterior end.
SIDE: Ambitus: Unique oblique slope; begins just below center on anterior end and slopes low below truncation on posterior end.
Side shape: Highly inflated; apex at center. Anterior end rounded; posterior end vertically truncated and slanted.
BOTTOM: Bottom shape: Inflated.
AMB: Amb shape: Unpaired ambulacrum (III) in wide, deep sulcus with high sloping sides.
Amb arrangement: Paired ambs petaloid, open-ended. Anterior paired ambs flexuous (curved) and twice the length of the posterior pair. Posterior pair shorter.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores heterogeneous (Enallaster-type): alternating sets of slit-like pores and round pore pairs.
Paired ambs: Pore pairs in upper series; large slits in lower series; open-ended.
TUBERCLES: Distribution: Small, scattered. Thicker near outer margins and aboral surface; plastron thickest.
APICAL SYSTEM: Location: Slightly posterior of midpoint.
Type: Ethmophract.
Genital pores: Four gonopores.
PERIPROCT (ANUS): Shape & Size: Small, rhombic (diamond-shaped); pointed down; equally wide and tall.
Location: Above midpoint on truncated posterior face.
Visibility: Visible from posterior view.
PERISTOME (MOUTH): Shape: Pentagonal; wider than tall.
Orientation: Facing downward/anteriorly.
Visibility: Visible from anterior end.
SPECIMENS STUDIED & CONDITION: Three specimens studied. Holotype NPL 94332; Paratype NPL 94333. Found by Dr. Steven Crane.
ETYMOLOGY
Fossils named after Brewster County, Texas, where the specimens were found.
REMARKS & COMPARISONS
Comparisons:
Plate: HeBr-10
Series: Upper Cretaceous Group: Washita Formation: Del Rio
Locale: Buck Hill County: Brewster Stage: Cenomanian
Length: 35.6 mm Width: 33.7 mm Height: 29.2 mm
Specimen in photo: NPL 94332 Holotype
Collector: Dr. Steven Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94332
Paratypes: NPL 94333
Locality: Buck Hill, Brewster County, Texas
Stratigraphy: Del Rio Formation, Washita Group
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 brewsterensis Thompson, 2020
TYPE SPECIES: Spatangus oblongus Brongniart, 1821
DIAGNOSIS
An inflated Heteraster from the Del Rio Formation of Brewster County, Texas. Unlike any Heteraster of Texas, distinguished by an ambitus that slopes the entire length of the test (oblique ambitus).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Del Rio Formation
Stratigraphic Units: Upper Cretaceous, Cenomanian
Counties: Brewster
DESCRIPTION
TOP: Length, width, height: 35.6 mm L × 33.7 mm W × 29.2 mm H.
Top shape: Cordate (heart-shaped); greatest width anterior of center.
Top domed: Deep sulcus on anterior end; flat at posterior end.
SIDE: Ambitus: Unique oblique slope; begins just below center on anterior end and slopes low below truncation on posterior end.
Side shape: Highly inflated; apex at center. Anterior end rounded; posterior end vertically truncated and slanted.
BOTTOM: Bottom shape: Inflated.
AMB: Amb shape: Unpaired ambulacrum (III) in wide, deep sulcus with high sloping sides.
Amb arrangement: Paired ambs petaloid, open-ended. Anterior paired ambs flexuous (curved) and twice the length of the posterior pair. Posterior pair shorter.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores heterogeneous (Enallaster-type): alternating sets of slit-like pores and round pore pairs.
Paired ambs: Pore pairs in upper series; large slits in lower series; open-ended.
TUBERCLES: Distribution: Small, scattered. Thicker near outer margins and aboral surface; plastron thickest.
APICAL SYSTEM: Location: Slightly posterior of midpoint.
Type: Ethmophract.
Genital pores: Four gonopores.
PERIPROCT (ANUS): Shape & Size: Small, rhombic (diamond-shaped); pointed down; equally wide and tall.
Location: Above midpoint on truncated posterior face.
Visibility: Visible from posterior view.
PERISTOME (MOUTH): Shape: Pentagonal; wider than tall.
Orientation: Facing downward/anteriorly.
Visibility: Visible from anterior end.
SPECIMENS STUDIED & CONDITION: Three specimens studied. Holotype NPL 94332; Paratype NPL 94333. Found by Dr. Steven Crane.
ETYMOLOGY
Fossils named after Brewster County, Texas, where the specimens were found.
REMARKS & COMPARISONS
Comparisons:
- H. aguilerai: H. brewsterensis resembles Heteraster aguilerai (Böse, 1910) in general petal arrangement, but differs by having a much rounder/inflated adoral surface, a more steeply sloping anterior profile, and the unique, non-level (sloping) ambitus.
