Holaster simplex Shumard, 1853
Plate: HoSi-10
Series: Lower Cretaceous Group: Washita Formation: Fort Worth
Locale: Preston County: Grayson Stage: Albian
Length: 51.7 mm Width: 44.5 mm Height: 31.5 mm
Specimen in photo: Collection of Ed Elliott
Plate: HoSi-20
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Madill, Oklahoma County: Marshall, Oklahoma
Length: 50.1 mm Width: 41.4 mm Height: 34.5 mm
Specimen in photo: Collection of Frank Crane
Flexible plated surface which encloses the anus.
HOLOTYPE INFO:
Holotype: Originally described by Shumard (1853) from Fort Washita, Oklahoma. The type material is likely lost (common for Shumard types).
Locality: Fort Washita, near present-day Durant, Oklahoma.
Stratigraphy: "Marly clay of the Red River" (Duck Creek Formation equivalent).
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 simplex Shumard, 1853
TYPE SPECIES: Spatangus nodulosus Goldfuss, 1829
DIAGNOSIS
Test oblong-cordiform; upper surface much elevated and rounded with a shallow anterior groove; lower surface flat. Apical system compact and not greatly elongated. Peristome transversely oval and anterior; periproct large on the truncated posterior margin (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Fort Worth, Duck Creek, Weno, Denton
Stratigraphic Units: Lower Cretaceous, Albian
Counties: Grayson (TX), Marshall (OK)
Abundance: Common in the Washita Group.
DESCRIPTION
TOP: Length, width, height: 51.7 mm L × 44.5 mm W × 31.5 mm H (HoSi-10).
Top shape: Oblong, cordate (heart-shaped). A shallow groove occupies the anterior face, producing a feeble emargination of the anterior ambitus (Clark & Twitchell, 1915).
Top domed: Much elevated and rounded above (Clark & Twitchell, 1915). A slight ridge extends along the central suture of the posterior interambulacrum (5) (Clark & Twitchell, 1915).
SIDE: Side shape: Rounded above and flattened below.
Profile: Variable; some individuals are high and globose, others low and flat (Clark & Twitchell, 1915). The posterior margin is suddenly truncated (Clark & Twitchell, 1915).
BOTTOM: Bottom shape: Flattened.
AMB: Amb shape: Ambulacra are wide.
Amb arrangement: Posterior paired ambulacra are bent more or less forward in their upper portions; anterior paired ambulacra are bent slightly backward (Clark & Twitchell, 1915).
PORE PAIRS: Arrangement: Unigeminal.
Shape: Paired ambulacra have slit-like/elongated openings in the upper portion, becoming very small and indistinct toward the margin and base. Pores of the unpaired ambulacrum are exceedingly small (Clark & Twitchell, 1915).
TUBERCLES: Distribution: Surface of both interambulacral and ambulacral plates covered by small tubercles (Clark & Twitchell, 1915).
GRANULES: Distribution: Numerous microscopic granules located between the tubercles (Clark & Twitchell, 1915).
FASCIOLE: Absent.
APICAL SYSTEM: Location: Apex nearly central (Clark & Twitchell, 1915).
Shape: Compact and rather short (not greatly elongated).
Plating: The four genital plates are large and broad. Two oculars are large and interposed; the remaining three are very small (Clark & Twitchell, 1915).
PERIPROCT (ANUS): Shape: Large, oval, and acuminate (pointed) above (Clark & Twitchell, 1915).
Location: Situated on the truncated posterior border.
Features: In Specimen 2 (HoSi-20), the flexible plated surface enclosing the anus is preserved, protruding outward and covering the entire periproct. This is a rare preservational feature.
PERISTOME (MOUTH): Shape: Large, transversely oval/oblong.
Location: Situated near the anterior margin (Clark & Twitchell, 1915).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
ETYMOLOGY
From the Latin simplex, likely referring to the simple, unadorned nature of the test compared to more ornate echinoids.
REMARKS & COMPARISONS
Remarks: Clark & Twitchell (1915) noted that the variations in this species are very pronounced (high/globose vs. low/flat) and found no satisfactory criteria to recognize the separate species established by Marcou (H. comanchesi) and Cragin (H. nanus) at that time. Cooke (1946) later synonymized H. simplex with the European Holaster laevis.
Comparisons:
Plate: HoSi-10
Series: Lower Cretaceous Group: Washita Formation: Fort Worth
Locale: Preston County: Grayson Stage: Albian
Length: 51.7 mm Width: 44.5 mm Height: 31.5 mm
Specimen in photo: Collection of Ed Elliott
Plate: HoSi-20
Series: Lower Cretaceous Group: Washita Formation: Duck Creek
Locale: Madill, Oklahoma County: Marshall, Oklahoma
Length: 50.1 mm Width: 41.4 mm Height: 34.5 mm
Specimen in photo: Collection of Frank Crane
Flexible plated surface which encloses the anus.
HOLOTYPE INFO:
Holotype: Originally described by Shumard (1853) from Fort Washita, Oklahoma. The type material is likely lost (common for Shumard types).
Locality: Fort Washita, near present-day Durant, Oklahoma.
Stratigraphy: "Marly clay of the Red River" (Duck Creek Formation equivalent).
SYNONYMY
- Holaster simplex Shumard, 1853
- Holaster comanchesi Marcou, 1858 (regarded as synonym by Clark & Twitchell, 1915) (I do not agree.)
- Holaster laevis (Brongniart, 1822) (fide Cooke, 1946) (I do not agree.)
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 simplex Shumard, 1853
TYPE SPECIES: Spatangus nodulosus Goldfuss, 1829
DIAGNOSIS
Test oblong-cordiform; upper surface much elevated and rounded with a shallow anterior groove; lower surface flat. Apical system compact and not greatly elongated. Peristome transversely oval and anterior; periproct large on the truncated posterior margin (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Fort Worth, Duck Creek, Weno, Denton
Stratigraphic Units: Lower Cretaceous, Albian
Counties: Grayson (TX), Marshall (OK)
Abundance: Common in the Washita Group.
DESCRIPTION
TOP: Length, width, height: 51.7 mm L × 44.5 mm W × 31.5 mm H (HoSi-10).
Top shape: Oblong, cordate (heart-shaped). A shallow groove occupies the anterior face, producing a feeble emargination of the anterior ambitus (Clark & Twitchell, 1915).
Top domed: Much elevated and rounded above (Clark & Twitchell, 1915). A slight ridge extends along the central suture of the posterior interambulacrum (5) (Clark & Twitchell, 1915).
SIDE: Side shape: Rounded above and flattened below.
Profile: Variable; some individuals are high and globose, others low and flat (Clark & Twitchell, 1915). The posterior margin is suddenly truncated (Clark & Twitchell, 1915).
BOTTOM: Bottom shape: Flattened.
AMB: Amb shape: Ambulacra are wide.
Amb arrangement: Posterior paired ambulacra are bent more or less forward in their upper portions; anterior paired ambulacra are bent slightly backward (Clark & Twitchell, 1915).
PORE PAIRS: Arrangement: Unigeminal.
Shape: Paired ambulacra have slit-like/elongated openings in the upper portion, becoming very small and indistinct toward the margin and base. Pores of the unpaired ambulacrum are exceedingly small (Clark & Twitchell, 1915).
TUBERCLES: Distribution: Surface of both interambulacral and ambulacral plates covered by small tubercles (Clark & Twitchell, 1915).
GRANULES: Distribution: Numerous microscopic granules located between the tubercles (Clark & Twitchell, 1915).
FASCIOLE: Absent.
APICAL SYSTEM: Location: Apex nearly central (Clark & Twitchell, 1915).
Shape: Compact and rather short (not greatly elongated).
Plating: The four genital plates are large and broad. Two oculars are large and interposed; the remaining three are very small (Clark & Twitchell, 1915).
PERIPROCT (ANUS): Shape: Large, oval, and acuminate (pointed) above (Clark & Twitchell, 1915).
Location: Situated on the truncated posterior border.
Features: In Specimen 2 (HoSi-20), the flexible plated surface enclosing the anus is preserved, protruding outward and covering the entire periproct. This is a rare preservational feature.
PERISTOME (MOUTH): Shape: Large, transversely oval/oblong.
Location: Situated near the anterior margin (Clark & Twitchell, 1915).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
- Plate HoSi-10: Collection of Ed Elliott. Length 51.7 mm. Fort Worth Formation.
- Plate HoSi-20: Collection of Frank Crane. Length 50.1 mm. Duck Creek Formation. Exceptional preservation of periproctal plating.
ETYMOLOGY
From the Latin simplex, likely referring to the simple, unadorned nature of the test compared to more ornate echinoids.
REMARKS & COMPARISONS
Remarks: Clark & Twitchell (1915) noted that the variations in this species are very pronounced (high/globose vs. low/flat) and found no satisfactory criteria to recognize the separate species established by Marcou (H. comanchesi) and Cragin (H. nanus) at that time. Cooke (1946) later synonymized H. simplex with the European Holaster laevis.
Comparisons:
- H. laevis var. planus: Clark & Twitchell (1915) stated H. simplex is very similar to this European form.
