Macraster pseudoelegans Adkins, 1930
Plate: MaPs-10
Series: Lower Cretaceous Group: Washita Formation: Fort Worth
Locale: Denison County: Grayson Stage: Albian
Length: 42.7 mm Width: 40.6 mm Height: 30.9 mm
Specimen in photos: Collection of Ed Elliott
Repository: Private Collection
HOLOTYPE INFO:
Holotype: UT 10565 (BEG/NPL) (Adkins, 1930).
Locality: Fort Worth, Tarrant County, Texas.
Stratigraphy: Fort Worth Limestone, 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 pseudoelegans Adkins, 1930
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A Macraster characterized by a tall, inflated test with a prominent posterior keel. The paired ambulacra are long, flexuous, and deeply sunken. Distinguished from M. elegans (in the strict sense) by its greater relative height and more angular contour (Adkins, 1930).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson, Tarrant.
Abundance: Common in the Fort Worth Limestone.
DESCRIPTION
TOP: Length, width, height: 42.7 mm L × 40.6 mm W × 30.9 mm H.
Top shape: Cordate and wide; angular anteriorly, narrowing posteriorly.
Top domed: Apex situated just posterior of center.
SIDE: Ambitus: Positioned about 40% of height from the base.
Side shape: Very inflated.
Profile: Anterior end is large and sloping; posterior end is long and vertically truncated.
BOTTOM: Bottom shape: Slightly curved.
AMB: Amb shape: All 5 ambulacra are sunken; the unpaired ambulacrum is slightly deeper (though still
shallow) and lanceolate.
Amb arrangement: Paired ambulacra are wide, flexuous, and open-ended.
Lengths: Anterior paired ambulacra are approximately 1.3 times (1 & 1/3) longer than the posterior pair.
Unpaired Amb: Narrower than the paired ambulacra.
INTERAMB: Shape: Raised.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores are arranged en chevron.
Shape: Pores in paired ambulacra are elongated. In the unpaired ambulacrum, they are slightly elongated.
TUBERCLES: Distribution: More pronounced on the adoral surface and around the apical system.
GRANULES: Distribution: More pronounced adorally.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Plating: Small madreporite.
PERIPROCT (ANUS): Shape: Small; longitudinally oval with pointed ends.
Location: Situated on the small truncated posterior face, just above the midpoint (50% from base).
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Subpentagonal; wide.
Size: Depressed; about equal in size to the periproct.
Visibility: Barely visible from the anterior end.
Plastron: Large.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Ed Elliott.
ETYMOLOGY
Named pseudoelegans ("false elegans") due to its strong resemblance to Macraster elegans, with which it was frequently confused (Adkins, 1930).
REMARKS & COMPARISONS
Remarks: Kamyabi Shadan et al. (2014) consider M. pseudoelegans to be a synonym of Macraster elegans (Shumard, 1853). They argue that the variations in test shape (height, angularity) used by Adkins to separate species like pseudoelegans, obesus, and nodopyga are likely ecophenotypic variations within a single biological species influenced by sedimentary environments.
Comparisons:
Plate: MaPs-10
Series: Lower Cretaceous Group: Washita Formation: Fort Worth
Locale: Denison County: Grayson Stage: Albian
Length: 42.7 mm Width: 40.6 mm Height: 30.9 mm
Specimen in photos: Collection of Ed Elliott
Repository: Private Collection
HOLOTYPE INFO:
Holotype: UT 10565 (BEG/NPL) (Adkins, 1930).
Locality: Fort Worth, Tarrant County, Texas.
Stratigraphy: Fort Worth Limestone, Washita Group.
SYNONYMY
- Macraster elegans (Shumard, 1853) (fide Kamyabi Shadan et al., 2014)
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 pseudoelegans Adkins, 1930
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A Macraster characterized by a tall, inflated test with a prominent posterior keel. The paired ambulacra are long, flexuous, and deeply sunken. Distinguished from M. elegans (in the strict sense) by its greater relative height and more angular contour (Adkins, 1930).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Grayson, Tarrant.
Abundance: Common in the Fort Worth Limestone.
DESCRIPTION
TOP: Length, width, height: 42.7 mm L × 40.6 mm W × 30.9 mm H.
Top shape: Cordate and wide; angular anteriorly, narrowing posteriorly.
Top domed: Apex situated just posterior of center.
SIDE: Ambitus: Positioned about 40% of height from the base.
Side shape: Very inflated.
Profile: Anterior end is large and sloping; posterior end is long and vertically truncated.
BOTTOM: Bottom shape: Slightly curved.
AMB: Amb shape: All 5 ambulacra are sunken; the unpaired ambulacrum is slightly deeper (though still
shallow) and lanceolate.
Amb arrangement: Paired ambulacra are wide, flexuous, and open-ended.
Lengths: Anterior paired ambulacra are approximately 1.3 times (1 & 1/3) longer than the posterior pair.
Unpaired Amb: Narrower than the paired ambulacra.
INTERAMB: Shape: Raised.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores are arranged en chevron.
Shape: Pores in paired ambulacra are elongated. In the unpaired ambulacrum, they are slightly elongated.
TUBERCLES: Distribution: More pronounced on the adoral surface and around the apical system.
GRANULES: Distribution: More pronounced adorally.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Plating: Small madreporite.
PERIPROCT (ANUS): Shape: Small; longitudinally oval with pointed ends.
Location: Situated on the small truncated posterior face, just above the midpoint (50% from base).
Visibility: Barely visible from above.
PERISTOME (MOUTH): Shape: Subpentagonal; wide.
Size: Depressed; about equal in size to the periproct.
Visibility: Barely visible from the anterior end.
Plastron: Large.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Ed Elliott.
ETYMOLOGY
Named pseudoelegans ("false elegans") due to its strong resemblance to Macraster elegans, with which it was frequently confused (Adkins, 1930).
REMARKS & COMPARISONS
Remarks: Kamyabi Shadan et al. (2014) consider M. pseudoelegans to be a synonym of Macraster elegans (Shumard, 1853). They argue that the variations in test shape (height, angularity) used by Adkins to separate species like pseudoelegans, obesus, and nodopyga are likely ecophenotypic variations within a single biological species influenced by sedimentary environments.
Comparisons:
- M. elegans: Adkins originally distinguished M. pseudoelegans by its taller profile and more flexuous petals compared to the "typical" flattened M. elegans.
