Goniophorus mainstreetensis Thompson, 2020
Plate: GoMa-10
Series: Upper Cretaceous Group: Washita Formation: Main Street
Locale: Trophy Club County: Denton Stage: Cenomanian
Length: 19.8 mm Width: 16.1 mm
Collection: Dr. Steven Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94326 — Non-vertebrate Paleontology Laboratory, University of Texas
Locality: Trophy Club, Denton County, Texas
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Carinacea Kroh & Smith, 2010
Superorder: Calycina Gregory, 1900
Order: Salenioida Delage & Hérouard, 1903
Family: Saleniidae L. Agassiz, 1838
Subfamily: Hyposaleniinae Mortensen, 1934
Genus: GONIOPHORUS L. Agassiz, 1838
Species: Goniophorus mainstreetensis Thompson, 2020
TYPE SPECIES: Goniophorus lunulatus L. Agassiz, 1838
DIAGNOSIS
Extremely large Goniophorus from Washita Group, with triangular periproct, dome shaped, large tubercles, with small granules on genital and ocular plates, very minute scrobicular tubercles at horizontally suture between interambulacral plates, crowded ambulacral tubercles above ambitus, and large interambulacral plates are wider than tall .
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Main Street Formation
Stratigraphic Units: Upper Cretaceous, Cenomanian
Counties: Denton County
DESCRIPTION
TOP: Length, width, height: 19.8 mm L × 16.1 mm H
Top shape: Round from above
Top domed: Dome shaped; apical system not raised from test except periproct
SIDE: Ambitus: At midpoint
Side shape: Very inflated
BOTTOM: Bottom flat: Bottom flat; slightly convex
AMB: Amb shape: Lanceolate; flexuous until reaching adoral surface. Narrowing at apical disk and slightly at peristome
Amb primary tubercles: Two rows of staggered tubercles down center; above ambitus they crowd and touch; at adoral surface they widen with two rows of granules. Do not increase in size until nearing peristome
Sphaeridial pits: Present in ambulacra, on oral surface, away from the peristome
INTERAMB: Interamb width: Almost 4 times wider than ambulacra
Interamb plating: Alternating plates; large plates wider than tall. Plates widen at interradial suture and thicken with granules near poles. Adoral plates very small, crowded with scrobicular tubercles
Interamb primary tubercles: Two rows of staggered tubercles (6 to 7 in each row); decreasing in size near apical disk and peristome
PORE PAIRS: Shape: Round to oval
Arrangement: Bigeminate adorally and unigeminate at ambitus and aborally; offset
TUBERCLES: Primary Perforated: Imperforate
Primary Crenulate: Yes; distinctively crenulate
Primary Boss: Large, raised
Primary Mamelon: Large, rounded upon large platforms
Secondary tubercles: Scrobicular tubercles very minute at horizontal suture between interambulacral plates; primary tubercles have contiguous scrobicular circles, mostly naked at upper and lower borders of plates
APICAL SYSTEM: Size: Large (9.1 mm); close to 46% of test from top
Shape: Scallop shaped; sits mostly flat on corona
Plates: 5 oculars, 5 genitals, 1 suranal. Genitals 8-sided. Oculars fat, pointed on ends and center, indented at ambulacra
Ornamentation: Genital and ocular plates have small granules
Genital pores: Each genital plate perforated
PERIPROCT (ANUS): Shape & Size: Triangular; 4.4 mm wide × 4.1 mm tall
PERISTOME (MOUTH): Size: Large (7.5 mm); about 37.8% of base
Shape: Rounded
Lip: Notches extremely small
SPECIMENS STUDIED & CONDITION: Several specimens studied. Holotype NPL 94326 .
ETYMOLOGY: Named after the formation from which it is found - Main Street. .
REMARKS & COMPARISONS
Remarks: Goniophorus mainstreetensis has crowded ambulacral tubercles and adoral interambulacral plates very thick with granules, unlike other Goniophorus species.
Comparisons:
Plate: GoMa-10
Series: Upper Cretaceous Group: Washita Formation: Main Street
Locale: Trophy Club County: Denton Stage: Cenomanian
Length: 19.8 mm Width: 16.1 mm
Collection: Dr. Steven Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94326 — Non-vertebrate Paleontology Laboratory, University of Texas
Locality: Trophy Club, Denton County, Texas
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Carinacea Kroh & Smith, 2010
Superorder: Calycina Gregory, 1900
Order: Salenioida Delage & Hérouard, 1903
Family: Saleniidae L. Agassiz, 1838
Subfamily: Hyposaleniinae Mortensen, 1934
Genus: GONIOPHORUS L. Agassiz, 1838
Species: Goniophorus mainstreetensis Thompson, 2020
TYPE SPECIES: Goniophorus lunulatus L. Agassiz, 1838
DIAGNOSIS
Extremely large Goniophorus from Washita Group, with triangular periproct, dome shaped, large tubercles, with small granules on genital and ocular plates, very minute scrobicular tubercles at horizontally suture between interambulacral plates, crowded ambulacral tubercles above ambitus, and large interambulacral plates are wider than tall .
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Main Street Formation
Stratigraphic Units: Upper Cretaceous, Cenomanian
Counties: Denton County
DESCRIPTION
TOP: Length, width, height: 19.8 mm L × 16.1 mm H
Top shape: Round from above
Top domed: Dome shaped; apical system not raised from test except periproct
SIDE: Ambitus: At midpoint
Side shape: Very inflated
BOTTOM: Bottom flat: Bottom flat; slightly convex
AMB: Amb shape: Lanceolate; flexuous until reaching adoral surface. Narrowing at apical disk and slightly at peristome
Amb primary tubercles: Two rows of staggered tubercles down center; above ambitus they crowd and touch; at adoral surface they widen with two rows of granules. Do not increase in size until nearing peristome
Sphaeridial pits: Present in ambulacra, on oral surface, away from the peristome
INTERAMB: Interamb width: Almost 4 times wider than ambulacra
Interamb plating: Alternating plates; large plates wider than tall. Plates widen at interradial suture and thicken with granules near poles. Adoral plates very small, crowded with scrobicular tubercles
Interamb primary tubercles: Two rows of staggered tubercles (6 to 7 in each row); decreasing in size near apical disk and peristome
PORE PAIRS: Shape: Round to oval
Arrangement: Bigeminate adorally and unigeminate at ambitus and aborally; offset
TUBERCLES: Primary Perforated: Imperforate
Primary Crenulate: Yes; distinctively crenulate
Primary Boss: Large, raised
Primary Mamelon: Large, rounded upon large platforms
Secondary tubercles: Scrobicular tubercles very minute at horizontal suture between interambulacral plates; primary tubercles have contiguous scrobicular circles, mostly naked at upper and lower borders of plates
APICAL SYSTEM: Size: Large (9.1 mm); close to 46% of test from top
Shape: Scallop shaped; sits mostly flat on corona
Plates: 5 oculars, 5 genitals, 1 suranal. Genitals 8-sided. Oculars fat, pointed on ends and center, indented at ambulacra
Ornamentation: Genital and ocular plates have small granules
Genital pores: Each genital plate perforated
PERIPROCT (ANUS): Shape & Size: Triangular; 4.4 mm wide × 4.1 mm tall
PERISTOME (MOUTH): Size: Large (7.5 mm); about 37.8% of base
Shape: Rounded
Lip: Notches extremely small
SPECIMENS STUDIED & CONDITION: Several specimens studied. Holotype NPL 94326 .
ETYMOLOGY: Named after the formation from which it is found - Main Street. .
REMARKS & COMPARISONS
Remarks: Goniophorus mainstreetensis has crowded ambulacral tubercles and adoral interambulacral plates very thick with granules, unlike other Goniophorus species.
Comparisons:
- G. scotti: Shares the triangular periproct shape.
- G. graysonensis: G. mainstreetensis is more dome shaped, has a larger peristome with smaller notches, and the granules on the apical plates are smaller than in G. graysonensis .
