Eotiaris guadalupensis Thompson, Petsios, Davidson, Erkenbrack, Gao, & Bottjer, 2015
Plate: EoGu-10
Series: Permian Group: Leonard / Delaware Mtn Formation: Road Canyon / Bell Canyon
Locale: Glass Mountains County: Brewster / Culberson Stage: Roadian–Capitanian
Length: 9.51 mm (Fragment) Width: 8.14 mm (Fragment)
Specimens in photo: USNM 610600 (Holotype); USNM 610601-610605 (Paratypes)
Repository: National Museum of Natural History (NMNH), Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 610600 (Interambulacral column) — National Museum of Natural History, Smithsonian Institution (Thompson et al., 2015)
Locality: USNM Locality 728p, Road Canyon Formation, Glass Mountains, Texas (Thompson et al., 2015)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Miocidaridae Durham & Melville, 1957
Genus: EOTIARIS Lambert, 1900
Species: Eotiaris guadalupensis Thompson, Petsios, Davidson, Erkenbrack, Gao, & Bottjer, 2015
TYPE SPECIES: Eotiaris keyserlingi (Geinitz, 1848)
DIAGNOSIS
Small cidaroid with rigidly sutured interambulacral plates at the ambitus and adoral regions, but imbricate plates adapically. Tubercles are large, sunken, perforate, and crenulate. Spines are variable, ranging from straight to clavate (club-shaped) or bulbous, characterized by a diagonally oriented ridge bearing the first row of spinules (Thompson et al., 2015).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Leonard Group (Glass Mtns); Delaware Mountain Group (Guadalupe Mtns) (Thompson et al., 2015)
Formations: Road Canyon Formation; Word Formation; Bell Canyon Formation (Lamar Limestone Member) (Thompson et al., 2015)
Stratigraphic Units: Middle to Upper Permian (Roadian to Capitanian) (Thompson et al., 2015)
Counties: Brewster, Culberson (Thompson et al., 2015)
DESCRIPTION
TOP: Dimensions: Holotype (column) measures 8.14 mm W × 9.51 mm H. Estimated total test diameter 9.4 mm to 20.6 mm based on column width ratios (Thompson et al., 2015).
Top shape: Test regular and small (Thompson et al., 2015)
AMB: Amb arrangement: Unknown; likely beveling under interambulacral plates as interior adradial interambulacral plate edges are denticulate (Thompson et al., 2015)
INTERAMB: Interamb plating: Arranged in two rows. First 4–6 plates usually rigidly sutured; adapical plates likely imbricate (disarticulated). Plates pentagonal, 1.3 to 1.6 times as wide as high. Interior of plates slightly concave with 7–8 denticles per plate at ambitus (Thompson et al., 2015).
Interamb width: Columns range from 4.2 mm to 9.3 mm wide (Thompson et al., 2015)
TUBERCLES: Primary tubercles: Large, sunken, and confluent below ambitus.
Primary Perforated: Yes (Thompson et al., 2015)
Primary Crenulate: Yes (Thompson et al., 2015)
Primary Boss: Crenulate (Thompson et al., 2015)
Primary Mamelon: Undercut and perforate (Thompson et al., 2015)
Primary Areola shape: Sunken; 2.6 mm wide x 2.6 mm high on specimen USNM 610601 (Thompson et al., 2015)
Secondary tubercles: At ambitus, one row separates primary tubercles. On large specimens, about 4 rows of secondaries between tubercle and perradial suture, and 3 rows between tubercle and adradial suture. Reduced adorally to 1–2 rows (Thompson et al., 2015).
APICAL SYSTEM: Unknown; adapical plates not preserved articulated (Thompson et al., 2015)
PERISTOME (MOUTH): Lip: No buccal notches present (Thompson et al., 2015)
Condition: Plates unknown; apophyses present on most oral interambulacral plates (Thompson et al., 2015)
SPINES: Shape: Morphology variable: straight, tapering, clavate, or bulbous. Likely varied aborally to orally (Thompson et al., 2015).
Structure: Hollow distally (both bulbous and non-bulbous types) (Thompson et al., 2015)
Base: Prominent milled ring proximally. Acetabulum bears perforation and faint crenulations (Thompson et al., 2015).
Ornamentation: Proximal 1/4 to 1/3 of shaft smooth, ending in a diagonally oriented ridge containing the first row of spinules. Distal rows parallel to the first row (Thompson et al., 2015).
Dimensions: Club spine 3.95 mm L x 1.88 mm W; Other spine 10.32 mm L x 2.5 mm W .
SPECIMENS STUDIED & CONDITION
Specimen condition: Disarticulated interambulacral columns and spines. Silicified preservation. Holotype USNM 610600 (Thompson et al., 2015).
ETYMOLOGY: Named for the Guadalupe Mountains of west Texas, where the Lamar Member specimens were collected (Thompson et al., 2015).
REMARKS & COMPARISONS
Remarks: This species represents the oldest known cidaroid echinoid (Thompson et al., 2015). It was previously identified by Kier as Miocidaris sp. or misidentified as secondary spines of other taxa. The stratigraphic range extends from the Roadian to the Capitanian.
Comparisons:
Plate: EoGu-10
Series: Permian Group: Leonard / Delaware Mtn Formation: Road Canyon / Bell Canyon
Locale: Glass Mountains County: Brewster / Culberson Stage: Roadian–Capitanian
Length: 9.51 mm (Fragment) Width: 8.14 mm (Fragment)
Specimens in photo: USNM 610600 (Holotype); USNM 610601-610605 (Paratypes)
Repository: National Museum of Natural History (NMNH), Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 610600 (Interambulacral column) — National Museum of Natural History, Smithsonian Institution (Thompson et al., 2015)
Locality: USNM Locality 728p, Road Canyon Formation, Glass Mountains, Texas (Thompson et al., 2015)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Miocidaridae Durham & Melville, 1957
Genus: EOTIARIS Lambert, 1900
Species: Eotiaris guadalupensis Thompson, Petsios, Davidson, Erkenbrack, Gao, & Bottjer, 2015
TYPE SPECIES: Eotiaris keyserlingi (Geinitz, 1848)
DIAGNOSIS
Small cidaroid with rigidly sutured interambulacral plates at the ambitus and adoral regions, but imbricate plates adapically. Tubercles are large, sunken, perforate, and crenulate. Spines are variable, ranging from straight to clavate (club-shaped) or bulbous, characterized by a diagonally oriented ridge bearing the first row of spinules (Thompson et al., 2015).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Leonard Group (Glass Mtns); Delaware Mountain Group (Guadalupe Mtns) (Thompson et al., 2015)
Formations: Road Canyon Formation; Word Formation; Bell Canyon Formation (Lamar Limestone Member) (Thompson et al., 2015)
Stratigraphic Units: Middle to Upper Permian (Roadian to Capitanian) (Thompson et al., 2015)
Counties: Brewster, Culberson (Thompson et al., 2015)
DESCRIPTION
TOP: Dimensions: Holotype (column) measures 8.14 mm W × 9.51 mm H. Estimated total test diameter 9.4 mm to 20.6 mm based on column width ratios (Thompson et al., 2015).
Top shape: Test regular and small (Thompson et al., 2015)
AMB: Amb arrangement: Unknown; likely beveling under interambulacral plates as interior adradial interambulacral plate edges are denticulate (Thompson et al., 2015)
INTERAMB: Interamb plating: Arranged in two rows. First 4–6 plates usually rigidly sutured; adapical plates likely imbricate (disarticulated). Plates pentagonal, 1.3 to 1.6 times as wide as high. Interior of plates slightly concave with 7–8 denticles per plate at ambitus (Thompson et al., 2015).
Interamb width: Columns range from 4.2 mm to 9.3 mm wide (Thompson et al., 2015)
TUBERCLES: Primary tubercles: Large, sunken, and confluent below ambitus.
Primary Perforated: Yes (Thompson et al., 2015)
Primary Crenulate: Yes (Thompson et al., 2015)
Primary Boss: Crenulate (Thompson et al., 2015)
Primary Mamelon: Undercut and perforate (Thompson et al., 2015)
Primary Areola shape: Sunken; 2.6 mm wide x 2.6 mm high on specimen USNM 610601 (Thompson et al., 2015)
Secondary tubercles: At ambitus, one row separates primary tubercles. On large specimens, about 4 rows of secondaries between tubercle and perradial suture, and 3 rows between tubercle and adradial suture. Reduced adorally to 1–2 rows (Thompson et al., 2015).
APICAL SYSTEM: Unknown; adapical plates not preserved articulated (Thompson et al., 2015)
PERISTOME (MOUTH): Lip: No buccal notches present (Thompson et al., 2015)
Condition: Plates unknown; apophyses present on most oral interambulacral plates (Thompson et al., 2015)
SPINES: Shape: Morphology variable: straight, tapering, clavate, or bulbous. Likely varied aborally to orally (Thompson et al., 2015).
Structure: Hollow distally (both bulbous and non-bulbous types) (Thompson et al., 2015)
Base: Prominent milled ring proximally. Acetabulum bears perforation and faint crenulations (Thompson et al., 2015).
Ornamentation: Proximal 1/4 to 1/3 of shaft smooth, ending in a diagonally oriented ridge containing the first row of spinules. Distal rows parallel to the first row (Thompson et al., 2015).
Dimensions: Club spine 3.95 mm L x 1.88 mm W; Other spine 10.32 mm L x 2.5 mm W .
SPECIMENS STUDIED & CONDITION
Specimen condition: Disarticulated interambulacral columns and spines. Silicified preservation. Holotype USNM 610600 (Thompson et al., 2015).
ETYMOLOGY: Named for the Guadalupe Mountains of west Texas, where the Lamar Member specimens were collected (Thompson et al., 2015).
REMARKS & COMPARISONS
Remarks: This species represents the oldest known cidaroid echinoid (Thompson et al., 2015). It was previously identified by Kier as Miocidaris sp. or misidentified as secondary spines of other taxa. The stratigraphic range extends from the Roadian to the Capitanian.
Comparisons:
- Eotiaris keyserlingi: Very similar morphologically (rigid test, imbricate adapically, sunken/crenulate tubercles). E. guadalupensis differs by having clavate (club-shaped) spines and larger spinules on the spines; E. keyserlingi spines are smooth with smaller spinules and lack the clavate morphotype (Thompson et al., 2015).
- Eotiaris connorsi: E. connorsi has a test composed entirely of imbricate, non-rigid plates (unlike the rigid ambital plates of guadalupensis) and lacks densely packed scrobicular tubercles (Thompson et al., 2015).
