Macraster nodopyga Lambert, 1920
Plate: MaNo-10a
Series: Lower Cretaceous Group: Washita Formation: Fort Worth
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 48.1 mm Width: 43.9 mm Height: 26.9 mm
Specimen in photos: BEG 34073 Hypotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: Described by Lambert (1920). Type material likely housed in the MNHN (Paris) or lost.
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 nodopyga Lambert, 1920
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A Macraster characterized by a cordate, anteriorly angular test that narrows posteriorly. Distinguished by a nodose protrusion on the posterior face near the periproct (implied by name) and specific ambulacral dimensions (Lambert, 1920).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant.
Abundance: Common in the Fort Worth area.
DESCRIPTION
TOP: Length, width, height: 48.1 mm L × 43.9 mm W × 26.9 mm H.
Top shape: Cordate; angular anteriorly, narrowing posteriorly.
Top domed: Apex situated approximately 30% from the posterior end (posterior of center).
SIDE: Ambitus: Positioned about 40% of height from the bottom.
Side shape: Sides inflated and curved.
Profile: Posterior end truncated; anterior end narrower and sloping.
BOTTOM: Bottom shape: Curved.
AMB: Amb shape: All 5 ambulacra are depressed, lanceolate, and open-ended.
Amb arrangement: Paired ambulacra are approximately equal in length, with the posterior pair being slightly longer.
Unpaired Amb: Sulcus is not very deep.
PORE PAIRS: Arrangement: Pores in the unpaired ambulacrum are small, slightly elongated, and arranged en chevron. Posterior pore pairs in the posterior ambulacra are also arranged en chevron.
Shape: Pores in paired ambulacra are elongated.
TUBERCLES: Distribution: Small. Tuberculation is more pronounced on the adoral surface and at the margins.
GRANULES: Distribution: More pronounced adorally and marginally.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Plating: Madreporite constitutes about 1/3 of the apical system.
PERIPROCT (ANUS): Shape: Small; longitudinally oval with pointed ends.
Location: Situated at the midpoint of the posterior truncation.
Visibility: Not visible from above.
PERISTOME (MOUTH): Shape: Transversely subpentagonal.
Size: Larger than the periproct.
Visibility: Barely visible from the posterior end.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype BEG 21499.
ETYMOLOGY
From the Latin nodus (knot/node) and Greek pyge (rump/buttocks), referring to the shape of the posterior truncation.
REMARKS & COMPARISONS
Remarks: Kamyabi Shadan et al. (2014) regard M. nodopyga as a synonym of Macraster elegans (Shumard, 1853). They conclude that the numerous species names assigned to large, inflated Macraster from the USA and Mexico are likely overestimations based on local ecophenotypic variants influenced by sedimentary environments.
Plate: MaNo-10a
Series: Lower Cretaceous Group: Washita Formation: Fort Worth
Locale: Fort Worth County: Tarrant Stage: Albian
Length: 48.1 mm Width: 43.9 mm Height: 26.9 mm
Specimen in photos: BEG 34073 Hypotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: Described by Lambert (1920). Type material likely housed in the MNHN (Paris) or lost.
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 nodopyga Lambert, 1920
TYPE SPECIES: Macraster texanus Roemer, 1888
DIAGNOSIS
A Macraster characterized by a cordate, anteriorly angular test that narrows posteriorly. Distinguished by a nodose protrusion on the posterior face near the periproct (implied by name) and specific ambulacral dimensions (Lambert, 1920).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Fort Worth Limestone.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Tarrant.
Abundance: Common in the Fort Worth area.
DESCRIPTION
TOP: Length, width, height: 48.1 mm L × 43.9 mm W × 26.9 mm H.
Top shape: Cordate; angular anteriorly, narrowing posteriorly.
Top domed: Apex situated approximately 30% from the posterior end (posterior of center).
SIDE: Ambitus: Positioned about 40% of height from the bottom.
Side shape: Sides inflated and curved.
Profile: Posterior end truncated; anterior end narrower and sloping.
BOTTOM: Bottom shape: Curved.
AMB: Amb shape: All 5 ambulacra are depressed, lanceolate, and open-ended.
Amb arrangement: Paired ambulacra are approximately equal in length, with the posterior pair being slightly longer.
Unpaired Amb: Sulcus is not very deep.
PORE PAIRS: Arrangement: Pores in the unpaired ambulacrum are small, slightly elongated, and arranged en chevron. Posterior pore pairs in the posterior ambulacra are also arranged en chevron.
Shape: Pores in paired ambulacra are elongated.
TUBERCLES: Distribution: Small. Tuberculation is more pronounced on the adoral surface and at the margins.
GRANULES: Distribution: More pronounced adorally and marginally.
FASCIOLE: Absent in Macraster.
APICAL SYSTEM: Size: Small.
Plating: Madreporite constitutes about 1/3 of the apical system.
PERIPROCT (ANUS): Shape: Small; longitudinally oval with pointed ends.
Location: Situated at the midpoint of the posterior truncation.
Visibility: Not visible from above.
PERISTOME (MOUTH): Shape: Transversely subpentagonal.
Size: Larger than the periproct.
Visibility: Barely visible from the posterior end.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype BEG 21499.
ETYMOLOGY
From the Latin nodus (knot/node) and Greek pyge (rump/buttocks), referring to the shape of the posterior truncation.
REMARKS & COMPARISONS
Remarks: Kamyabi Shadan et al. (2014) regard M. nodopyga as a synonym of Macraster elegans (Shumard, 1853). They conclude that the numerous species names assigned to large, inflated Macraster from the USA and Mexico are likely overestimations based on local ecophenotypic variants influenced by sedimentary environments.
