Macraster texanus Roemer, 1888
Plate: MaTe-10
Series: Lower Cretaceous Group: Washita Formation: Georgetown
Locale: Georgetown County: Williamson Stage: Albian
Length: 77.3 mm Width: 73.2 mm Height: 39.1 mm
Specimen in photos: Collection of Ed Elliott
Repository: Private Collection
HOLOTYPE INFO:
Holotype: Roemer's original specimen is housed in the Geological Museum of the University of Wrocław (formerly Breslau), Poland.
Locality: Georgetown, Williamson County, Texas (Roemer, 1888).
Stratigraphy: "Vola Limestone" (Georgetown Formation equivalent), Washita Group.
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: Macrasteridae Lambert, 1920
Genus: MACRASTER Roemer, 1888
Species: Macraster texanus Roemer, 1888
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
Test large, cordate, and inflated. Characterized by deeply sunken ambulacra and the complete absence of fascioles (peripetalous or subanal). The posterior face is vertically truncated. Distinguished from Hemiaster by the lack of fascioles and the straight, non-flexuous ambulacra (Roemer, 1888).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Georgetown Formation; Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Williamson, Travis, Tarrant.
Abundance: Common in the Washita Group.
DESCRIPTION
TOP: Length, width, height: 77.3 mm L × 73.2 mm W × 39.1 mm H.
Top shape: Cordate; wide and narrowing posteriorly. Margin is very angular.
Top domed: Flat for 60% of the test surface, setting the apex.
SIDE: Ambitus: Positioned about 40% of height from the base.
Side shape: Inflated.
Profile: Posterior end is long and vertically truncated (almost perpendicular to base); anterior end is sloping.
BOTTOM: Bottom shape: Mostly flat; slightly curved.
AMB: Amb shape: All 5 ambulacra are sunken; the unpaired ambulacrum (III) is more deeply sunken and narrower than the paired ambulacra.
Amb arrangement: Paired ambulacra are wide, lanceolate, and open at the outer ends. Anterior paired ambulacra are slightly longer than the posterior pair and extend almost to the margin.
INTERAMB: Shape: Raised/convex.
PORE PAIRS: Shape: Pores in paired ambulacra are elongated. In the unpaired ambulacrum, pore pairs are slightly elongated.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes.
Areolas: Sunken.
Distribution: Small. Tuberculation and granulation are more pronounced on the adoral surface and at the margins of the aboral surface.
GRANULES: Distribution: See Tubercles section.
FASCIOLE: Absent. The genus Macraster was established by Roemer (1888) specifically for Hemiaster-like echinoids that lack a peripetalous fasciole.
APICAL SYSTEM: Location: Central.
Condition: Mostly missing in figured specimen.
Genital Pores: 4 gonopores (Roemer, 1888).
PERIPROCT (ANUS): Shape: Small; longitudinally oval.
Location: Situated on the small truncated posterior end, approximately 60% up from the base.
Visibility: Cannot be seen from above.
PERISTOME (MOUTH): Shape: Subpentagonal; wide.
Size: Depressed; about equal in size to the periproct.
Visibility: Barely visible from the anterior end.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Ed Elliott.
ETYMOLOGY
Named for the state of Texas, where the genus and species were first described (Roemer, 1888).
REMARKS & COMPARISONS
Remarks: Macraster texanus is the type species of the genus Macraster. Historically, it has been maintained as a distinct species from Macraster elegans (Shumard, 1853) based on Roemer's description, but modern revision by Cooke (1946) and Kamyabi Shadan et al. (2014) regards M. texanus as a junior synonym of M. elegans, citing that the variations in shape are ecophenotypic.
Comparisons:
Plate: MaTe-10
Series: Lower Cretaceous Group: Washita Formation: Georgetown
Locale: Georgetown County: Williamson Stage: Albian
Length: 77.3 mm Width: 73.2 mm Height: 39.1 mm
Specimen in photos: Collection of Ed Elliott
Repository: Private Collection
HOLOTYPE INFO:
Holotype: Roemer's original specimen is housed in the Geological Museum of the University of Wrocław (formerly Breslau), Poland.
Locality: Georgetown, Williamson County, Texas (Roemer, 1888).
Stratigraphy: "Vola Limestone" (Georgetown Formation equivalent), Washita Group.
SYNONYMY
- Hemiaster elegans Shumard, 1853 (fide Cooke, 1946; Kamyabi Shadan et al., 2014)
- Macraster texanus Roemer, 1888 (Type Species of Genus)
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: Macrasteridae Lambert, 1920
Genus: MACRASTER Roemer, 1888
Species: Macraster texanus Roemer, 1888
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
Test large, cordate, and inflated. Characterized by deeply sunken ambulacra and the complete absence of fascioles (peripetalous or subanal). The posterior face is vertically truncated. Distinguished from Hemiaster by the lack of fascioles and the straight, non-flexuous ambulacra (Roemer, 1888).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Georgetown Formation; Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Williamson, Travis, Tarrant.
Abundance: Common in the Washita Group.
DESCRIPTION
TOP: Length, width, height: 77.3 mm L × 73.2 mm W × 39.1 mm H.
Top shape: Cordate; wide and narrowing posteriorly. Margin is very angular.
Top domed: Flat for 60% of the test surface, setting the apex.
SIDE: Ambitus: Positioned about 40% of height from the base.
Side shape: Inflated.
Profile: Posterior end is long and vertically truncated (almost perpendicular to base); anterior end is sloping.
BOTTOM: Bottom shape: Mostly flat; slightly curved.
AMB: Amb shape: All 5 ambulacra are sunken; the unpaired ambulacrum (III) is more deeply sunken and narrower than the paired ambulacra.
Amb arrangement: Paired ambulacra are wide, lanceolate, and open at the outer ends. Anterior paired ambulacra are slightly longer than the posterior pair and extend almost to the margin.
INTERAMB: Shape: Raised/convex.
PORE PAIRS: Shape: Pores in paired ambulacra are elongated. In the unpaired ambulacrum, pore pairs are slightly elongated.
TUBERCLES: Primary Perforated: Yes.
Primary Crenulate: Yes.
Areolas: Sunken.
Distribution: Small. Tuberculation and granulation are more pronounced on the adoral surface and at the margins of the aboral surface.
GRANULES: Distribution: See Tubercles section.
FASCIOLE: Absent. The genus Macraster was established by Roemer (1888) specifically for Hemiaster-like echinoids that lack a peripetalous fasciole.
APICAL SYSTEM: Location: Central.
Condition: Mostly missing in figured specimen.
Genital Pores: 4 gonopores (Roemer, 1888).
PERIPROCT (ANUS): Shape: Small; longitudinally oval.
Location: Situated on the small truncated posterior end, approximately 60% up from the base.
Visibility: Cannot be seen from above.
PERISTOME (MOUTH): Shape: Subpentagonal; wide.
Size: Depressed; about equal in size to the periproct.
Visibility: Barely visible from the anterior end.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Ed Elliott.
ETYMOLOGY
Named for the state of Texas, where the genus and species were first described (Roemer, 1888).
REMARKS & COMPARISONS
Remarks: Macraster texanus is the type species of the genus Macraster. Historically, it has been maintained as a distinct species from Macraster elegans (Shumard, 1853) based on Roemer's description, but modern revision by Cooke (1946) and Kamyabi Shadan et al. (2014) regards M. texanus as a junior synonym of M. elegans, citing that the variations in shape are ecophenotypic.
Comparisons:
- Hemiaster: Macraster is distinguished from Hemiaster by the absence of fascioles.
