​Temnocidaris (Hirudocidaris) wenoensis Thompson, 2016
(Redescription Based on Newly Documented Test Material)
 
Plate: TehWe-10
Series: Lower Cretaceous                       Group: Washita                                       Formation: Weno
Locale: Fort Worth                                  County: Tarrant                                     Stage: Albian
Length: 25.5 mm (largest)                      Width: 5.0 mm (largest)
Specimen in photos:                               Collector: Frank Crane
NPL 83049                                              Spine.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
 
Plate: TehWe-20
Series: Lower Cretaceous                       Group: Washita                                       Formation: Weno
Locale: Pottsboro                                    County: Grayson                                   Stage: Albian
Length: 46.2 mm                                  Width: 32.7 mm
Specimen in photos:                               Collector: Lance Southwick
Repository:                                           Private Collection
 
ASSOCIATED MATERIAL: Test articulated with three primary spines
Matrix: Hard gray limestone
Preservation: Excellent; first known articulated test for the species
Repository: Private collection (specimen long known but unstudied)
 
HOLOTYPE INFORMATION (Spine‑Based Original Description)
Holotype: NPL 83049 (spine)
Locality: Fort Worth, Tarrant County, Texas
Stratigraphy: Weno Formation, Washita Group
 
SYNONYMY
• Temnocidaris (Hirudocidaris) wenoensis Thompson, 2016
 
SYSTEMATIC PALEONTOLOGY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Subfamily: Stereocidarinae Lambert, 1900
Genus: Temnocidaris Cotteau, 1863
Subgenus: Hirudocidaris Smith & Wright, 1989
Species: Temnocidaris (Hirudocidaris) wenoensis Thompson, 2016
Type species of subgenus: Cidaris hirudo Sorignet, 1850
 
EMENDED DIAGNOSIS
A species of Temnocidaris (Hirudocidaris) characterized by fusiform primary spines with strong beaded ornamentation and an exceptionally wide, strongly pronounced basal collar, greatly exceeding that of T. (H.) hirudo. The newly described test exhibits well‑developed scrobicular rings, a broad extrascrobicular zone of substantial secondary tubercles, sunken areoles, and large, deeply incised perforated bosses, all consistent with assignment to Hirudocidaris and distinct from Stereocidaris.
 
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formation: Weno Formation
Age: Lower Cretaceous (Albian)
Counties: Tarrant (holotype, spine), Grayson
Abundance: Previously known only from two spines. This is the first recognized test for the species.  In Grayson County, spines and plates are plentiful and tests are scarce.
 
DESCRIPTION
Test
Overall Form
Test moderately small, 46.2 × 32.7 mm, slightly elongate. Outline subcircular to weakly oval. Profile gently domed; ambitus moderately rounded.
 
Interambulacral Plates
  • Plates above the ambitus are large and bear a strongly developed scrobicular ring.
  • Extrascrobicular zone broad, consisting of numerous secondary tubercles:
    • First outer row is slightly enlarged,
    • Successive rows decrease in height and diameter,
    • Zone well‑developed rather than reduced to a single row.
  • Plate sculpture corresponds to the dense, coarse ornament typical of Hirudocidaris.
 
Primary Tubercles
  • Areoles: Deeply sunken, forming a recessed platform beneath the boss.
  • Bosses: Large, incised, perforated, non‑crenulate.
  • Boss architecture mirrors the exaggerated collar of the spines, producing a robust ball‑and‑socket articulation.
 
Scrobicular & Extrascrobicular Tubercles
  • Scrobicular tubercles fully encircle the primary tubercle, forming a strong scrobicular ring.
  • Extrascrobicular tubercles form a distinct zone, not merely a single row, separating this species from T. (S.) hudspethensis and other Stereocidaris forms.
 
Ambulacra
  • Ambulacra sinuous.
  • Poriferous zones narrow; pore pairs slightly oblique.
  • Interporiferous areas similar to the elongated wart + granule pattern seen in T. (S.) hudspethensis.
 
Apical System & Peristome
(Not fully preserved; ornamented granules present on remaining plates.)
Peristomial margin not exposed.
 
Spines (Holotype + Articulated Test)
  • Shape: Fusiform.
  • Ornamentation: Strong, evenly spaced beaded longitudinal ribs. Between the ribs in some of the troughs are also a row of beads that are the start of “new” ribs.  These “new” rows always have less bead count than the established ribs, sometimes 25 % less beads.  One unassociated 5.3 mm diameter spine had 25 rows of ribs of which 20 were established.  Larger unassociated spines 8.3 mm diameter do show a more fluted ornamentation, morphing from the beaded style.
  • Collar: Very wide, distinctly pronounced, forming a sharply expanded proximal swelling—diagnostic.
  • Neck: Narrow naked zone above the collar.
  • Tip: Distal end cup‑shaped.
  • Articulated spines match holotype in all features.
 
SPECIMENS STUDIED & CONDITION:
  1. Holotype: NPL 83049 (spine), Weno Formation, Tarrant County.
  2. Second spine specimen: Weno Formation, collected by Frank Crane.
  3. Test specimen: Pottsboro, Grayson County — first known test, articulated with three spines; excellent preservation.
 
ETYMOLOGY:
Named for the Weno Formation of the Washita Group.
 
REMARKS & COMPARISONS
Remarks
The newly documented test confirms the placement of T. (H.) wenoensis in Hirudocidaris, combining:
  • fusiform spines with strong beading,
  • an exceptionally enlarged basal collar,
  • dense extrascrobicular tubercle fields, but less than T. (S.) hudspethensis.
  • deeply sunken areoles, and
  • large, incised perforated bosses.
This morphology contrasts clearly with species of Stereocidaris, particularly those of the Washita Group.
 
Comparisons
  • Temnocidaris (Hirudocidaris) hirudo — Similar overall form but with a smaller, less pronounced collar and weaker beading on spines.
  • Temnocidaris (Stereocidaris) hudspethensis — Differs in:
    • below ambitus, extrascrobicular tubercles (single row vs. full zone),
    • spine form (cylindrical fluted vs. fusiform beaded),
    • secondary tubercles plate sculpture (sparce vs. dense).
Together, these features confirm that the Pottsboro specimen represents the first known articulated test of T. (H.) wenoensis and supports the species as valid and distinct.