Asteropyge sp.

 

This asteropygid is a devonian Trilobite coming from Bundenbach, Germany. As you will see it on the following pictures, Bundenbach means alot here :) I can't identify the specy right now as I do lack documentation on the Asteropygids of Bundenbach. No doubt that the exceptionnal preservation of this specimen could otherwise permit an accurate identification.

N.B : I haven't seen anywhere on the web an identified Asteropygid from bundenbach.

 

Specimen description:

  • Full prone trilobite
  • Ventral view.
  • On matrix
  • Slightly gold color.
  • Moderate lateral distorsion.
  • Ventral appendages on the posterior right part of the thorax.
  • Total size : 6.5 cm
  • Lower Devonian - Lower Emsian.
  • Hunsrück-Schiefern.
  • Bundenbach, Hunsrück.
  • Rheinland-Pfalz, Germany.
Complete view of the specimen
Zoom on the thorax and the appendages.

 

Diagnosis :

 

Order

 

 

 

 

 

 

 

 

 

Phacopida

 

 

 

 

 

 

 

 

 

SALTER 1864

 

 

 

 

 

 

 

 

 

Occurrence: Lower Ordovician (Tremadoc) to Upper Devonian (Famennian).

  • Cephalon: Proparian (Phacopina and Cheirurina), gonatoparian (Calymenina) or opisthoparian (Calymenina),
  • Preglabellar field often very short or absent.
  • 4 or fewer pairs of glabellar furrows.
  • Eyes : when present, schizochroal (Phacopina) or holochroal (Cheirurina and Calymenina).
  • With rostral plates (Calymenina and Cheirurina) or without (some Phacopina).
  • Hypostome conterminant (all suborders) to impendent (some devonian Phacopina).
  • Exosqueletton generally granulous.
  • Thorax: 8 – 19 segments, sometimes distinctly furrowed.
  • Axis sometimes broad (e.g., Homalonotidae).
  • Pygidium : Typically micropygous (most Calymenina and Phacopina), but variable (e.g., subisopygous in Dalmanitoidea and Acastoidea).
  • May be lobed or spiny (e.g., Cheirurina, some Dalmanitoidea, Acastoidea), or smooth-margined, with round or subtriangular outline (e.g., Calymenina, Phacopoidea).

Sub-order

 

 

 

 

 

Phacopina

 

 

 

 

 

STRUVE 1959

 

 

 

 

 
  • Cephalon : Proparian sutures (sometimes fused).
  • Schizochroal eyes.
  • Glabella expands forwards.
  • Librigena typically yoked as single piece.
  • Hypostome conterminant to impendent, some with no rostral plate.
  • Some with genal spines.
  • Thorax: 10 to (typically) 11 segments.
  • Pleurae furrowed, articulating facets distinct.
  • Rounded, angular, or spinose tips.
  • Pygidium : Typically smaller than cephalon (but subisopygous in Dalmanitoidea and Acastoidea).
  • Smooth or spinose.

Super-family

 

 

Acastoiedea

 

 

DELO 1935

 

 
  • Cephalon : Axial furrows slightly to moderately divergent.
  • Anterior glabellar lobes and furrows usually not fused (although furrows may be indistinct).
  • Eyes typically distant from posterior border furrows, but not strongly anterior.
  • Frontal glabellar lobe auxilliary impression system triangular in outline.
  • Maximum width of glabella adjacent to preglabellar furrow.
  • Median region of glabella devoid of muscle scars.
  • Cephalic margin "shouldered".
  • Laterally convex course of genal margin topographically distinct from curvature of axial margin.
  • Thorax : Pleural endings blunt, rounded or angular.
  • Sometimes spinose.
  • Pygidium : Micropygous to subisopygous.
  • Sometimes spinose (expressed as marginal spines).
  • Pygidial axis with deep, apodemal anterior ring furrows, with abrupt transition to shallow posterior ring furrows.
  • Coincident decrease in angle of axial furrow convergence.

Family

 

 

 

 

 

Acastidae

 

 

 

EDGECOMBE 1993

 

 

 

 
  • Cephalon : Semi-circular to rounded subtriangular.
  • Cephalic border narrow in front of the glabella.
  • Dorsal furrows slilghtly to moderately divergent.
  • Anterior glabellar furrows (S3) simple.
  • Medial furrows (S2) moderately deep.
  • Deep posterior furrows (S1).
  • L2 and L3 lateral glabellar lobes generally fused distally.
  • Muscle scars bearing sometimes callosities (Acastinae).
  • Eyes typically distant from the posterior genal furrows.
  • Hypostoma
  • Pygidium : micropygous to subisopygous.
  • Semi-circular to rounded subtriangular.
  • Short posterior spine present.

Sub-family

 Asteropyginae

DELO 1935

Traditionnally included in the Dalmanitidae, Asteropyginae are now included in the Acastids. Mostly benthic trilobites.

  • Cephalon : Closely similar to the Dalamanatid Dalmanitides BARRANDE 1853.
  • Glabella expanding forward.
  • 3 lateral glabellar furrows.
  • Eyes generally large.
  • Genal angles acutely pointed or bearing medium-length to very long genal spines in straight continuation of lateral margins.
  • Pygidium : Rachis never reaching the posterior region of the pygidial border.
  • Generally 5 pairs of lateral spines (sometimes 4 or 6).
  • Unpaired posterior lappet or spine.

Genus

 

Asteropyge

HAWLE & CORDA 1847

 
  • Cephalon : Slightly to moderately vaulted.
  • Border distinct.
  • No median process.
  • Glabellar frontal lobe sloping, fused with slightly elevated, transeversaly arched preglabellar field.
  • L2 and L3 lateral glabellar lobes detached axially.
  • L1 lobe considerably below level of L2 lobes.
  • S3 glabellar furrows only moderately oblique.
  • Occipital ring very prominent.
  • Palpebral lobes well above glabella.
  • Genal areas bordering eyes steeply sloping or even vertical.
  • Subocular ridges generally distinct.
  • Genal spines moderately to very long.
  • Thorax : With long pleural spines (type species).
  • pygidium : Slender axis with numerous rings (10 to 15)
  • Rings near front bent slightly forward and near rear not bent.
  • Pleural field with segmentation of supradevonica pattern.
  • 5 pairs of ribs (5th about as long as 1st).
  • 5 pairs of long, gently curved posterior pleural spines.
  • Posterior border produced in minute lappet or short spine.

Species

sp.

 

  

 

Complementary pictures :

 

Full specimen in B&W

Ventral appendages.

Pygidial segmentation : supradevonica

 

More specimens founded on the web :

 

Side view of Asteropyge sp. property of Indiana fossils.
Asteropyge sp. property of Indiana fossils.

 

Dorsal view of Asteropyge sp., property of Indiana fossils.
Asteropyge sp. (same specimen) property of Indiana fossils.

 

Precisions and remarks :

1 ) The pygidial segmentation has a prominent role in diffenciating the generas and species of Asteropygids (STRUVE, 1959) :

Prorotundifrons :

Prorotundifrons type (after PILLET, 1973).

 

Boothi :

Boothi type (after PILLET, 1973).

 

Supradevonica and cometa :
Supradevonica type (after PILLET, 1973).
Cometa type (after PILLET, 1973).

 

2) The Bundenbach trilobites and the ventral appendages...

There are several places in the world where the fossilization process permitted the preservation of the limbs or appendages. Half a billion of years later, you can now see some delicate ventral structures similar to shrimp limbs ! These appendages were both useful for the trilobite's locomotion and feeding, as for breathing as they wore gills, exactly as do the appendages of the actual arthropods. These famous places are the Burgess Shale, the Beecher's Bed and Bundenbach.

Please refer to the links page for more informations on the fossilization processes and on the appendages.

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