Holaster laevis (Brongniart, 1822)
Plate: HoLe-10
Series: Lower Cretaceous Group: Washita Formation: Georgetown
Locale: Osage Country: McLennan Stage: Albian
Length: 36.6 mm Width: 31.7 mm Height: 17.7 mm
Specimen in photo: NPL 83016 Hypotype
Collector: Terry Stephenson
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas Low Form.
HOLOTYPE INFO:
Holotype: Brongniart Collection (Repository uncertain, possibly MNHN Paris).
Locality: Mount Saint-Catherine, near Rouen, France (Brongniart, 1822).
Stratigraphy: "Craie chloritée" (Cenomanian).
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Holasteroida Durham, 1957
Family: Holasteridae Pictet, 1857
Genus: HOLASTER L. Agassiz, 1836
Species: Holaster laevis (Brongniart, 1822)
TYPE SPECIES: Spatangus nodulosus Goldfuss, 1829
DIAGNOSIS
Test cordate with a weak anterior sulcus and small posterior truncation. Upper surface strongly arched; lower surface nearly flat. Apical plates arranged in two longitudinal rows (elongate system). Ambulacra subpetaloid and flush; anterior pair curved slightly forward. No marginal fasciole (Cooke, 1953).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Georgetown Formation; Duck Creek, Fort Worth, Weno (as H. simplex in older Texas literature).
Stratigraphic Units: Lower Cretaceous, Albian
Counties: McLennan, Grayson, Tarrant, Pecos.
DESCRIPTION
TOP: Length, width, height: 36.6 mm L × 31.7 mm W × 17.7 mm H.
Top shape: Cordate outline. Anterior sulcus is weak/shallow.
Top domed: Upper surface strongly arched.
SIDE: Side shape: Profile variable (Low form in this specimen); posterior truncation is small.
BOTTOM: Bottom shape: Lower surface nearly flat.
AMB: Amb shape: Subpetaloid and flush with the test surface.
Amb arrangement: Anterior paired ambulacra are curved slightly forward; posterior paired ambulacra are straight. The anterior poriferous zone of each paired ambulacrum is narrower than the posterior zone (Cooke, 1953).
Unpaired Amb: Pores of the anterior unpaired ambulacrum (III) are very small, circular, and arranged in diagonal pairs.
INTERAMB: Shape: Plates large and smooth (implied by specific name laevis).
PORE PAIRS: Shape: Pores in paired ambulacra are oval.
TUBERCLES: Distribution: Tubercles generally small and fine, giving the test a smooth appearance (laevis = smooth).
GRANULES: Distribution: Not specified in source text, typically fine and dense.
FASCIOLE: Presence: There are no fascioles (Cooke, 1953). specifically, the absence of a marginal fasciole distinguishes Holaster from Cardiaster.
APICAL SYSTEM: Shape: Elongate.
Plating: Apical plates are arranged in two longitudinal rows headed by the anterior ocular (intercalary system).
PERIPROCT (ANUS): Location: Located at the top of a posterior truncation.
Visibility: Not visible from above.
PERISTOME (MOUTH): Shape: Transversely oval.
Location: Set far forward (anterior).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83016. Note on label indicates "Low Form." Collected by Terry Stephenson.
ETYMOLOGY
From the Latin laevis, meaning smooth, referring to the fine tuberculation and smooth appearance of the test.
REMARKS & COMPARISONS
Remarks: Cooke (1946, 1953) considered the common Texas species Holaster simplex Shumard to be a synonym of the European Holaster laevis. Texas specimens exhibit considerable variation in height, leading to distinction between "low forms" (like the specimen described here) and "high forms" (often referred to historically as Holaster supernus Cragin).
Comparisons:
Plate: HoLe-10
Series: Lower Cretaceous Group: Washita Formation: Georgetown
Locale: Osage Country: McLennan Stage: Albian
Length: 36.6 mm Width: 31.7 mm Height: 17.7 mm
Specimen in photo: NPL 83016 Hypotype
Collector: Terry Stephenson
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas Low Form.
HOLOTYPE INFO:
Holotype: Brongniart Collection (Repository uncertain, possibly MNHN Paris).
Locality: Mount Saint-Catherine, near Rouen, France (Brongniart, 1822).
Stratigraphy: "Craie chloritée" (Cenomanian).
SYNONYMY
- Spatangus laevis Brongniart, 1822
- Holaster simplex Shumard, 1853 (regarded as synonym by Cooke, 1946)
- Holaster comanchesi Marcou, 1858
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Holasteroida Durham, 1957
Family: Holasteridae Pictet, 1857
Genus: HOLASTER L. Agassiz, 1836
Species: Holaster laevis (Brongniart, 1822)
TYPE SPECIES: Spatangus nodulosus Goldfuss, 1829
DIAGNOSIS
Test cordate with a weak anterior sulcus and small posterior truncation. Upper surface strongly arched; lower surface nearly flat. Apical plates arranged in two longitudinal rows (elongate system). Ambulacra subpetaloid and flush; anterior pair curved slightly forward. No marginal fasciole (Cooke, 1953).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Georgetown Formation; Duck Creek, Fort Worth, Weno (as H. simplex in older Texas literature).
Stratigraphic Units: Lower Cretaceous, Albian
Counties: McLennan, Grayson, Tarrant, Pecos.
DESCRIPTION
TOP: Length, width, height: 36.6 mm L × 31.7 mm W × 17.7 mm H.
Top shape: Cordate outline. Anterior sulcus is weak/shallow.
Top domed: Upper surface strongly arched.
SIDE: Side shape: Profile variable (Low form in this specimen); posterior truncation is small.
BOTTOM: Bottom shape: Lower surface nearly flat.
AMB: Amb shape: Subpetaloid and flush with the test surface.
Amb arrangement: Anterior paired ambulacra are curved slightly forward; posterior paired ambulacra are straight. The anterior poriferous zone of each paired ambulacrum is narrower than the posterior zone (Cooke, 1953).
Unpaired Amb: Pores of the anterior unpaired ambulacrum (III) are very small, circular, and arranged in diagonal pairs.
INTERAMB: Shape: Plates large and smooth (implied by specific name laevis).
PORE PAIRS: Shape: Pores in paired ambulacra are oval.
TUBERCLES: Distribution: Tubercles generally small and fine, giving the test a smooth appearance (laevis = smooth).
GRANULES: Distribution: Not specified in source text, typically fine and dense.
FASCIOLE: Presence: There are no fascioles (Cooke, 1953). specifically, the absence of a marginal fasciole distinguishes Holaster from Cardiaster.
APICAL SYSTEM: Shape: Elongate.
Plating: Apical plates are arranged in two longitudinal rows headed by the anterior ocular (intercalary system).
PERIPROCT (ANUS): Location: Located at the top of a posterior truncation.
Visibility: Not visible from above.
PERISTOME (MOUTH): Shape: Transversely oval.
Location: Set far forward (anterior).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83016. Note on label indicates "Low Form." Collected by Terry Stephenson.
ETYMOLOGY
From the Latin laevis, meaning smooth, referring to the fine tuberculation and smooth appearance of the test.
REMARKS & COMPARISONS
Remarks: Cooke (1946, 1953) considered the common Texas species Holaster simplex Shumard to be a synonym of the European Holaster laevis. Texas specimens exhibit considerable variation in height, leading to distinction between "low forms" (like the specimen described here) and "high forms" (often referred to historically as Holaster supernus Cragin).
Comparisons:
- Cardiaster: Holaster is distinguished from Cardiaster by the absence of a marginal fasciole and the structure of the apical system.
- Pseudholaster: Distinguished by the lack of a marginal fasciole.
