Welsh holothurian bed: Tables

TABLE 1. Complete list of the fauna known from the Holothurian Bed at the time of writing; a total of ten sponge species and two dendroids are included, although the exact numbers may increase on further study. Abundance notes are semi-quantitative: "rare": encountered on three or fewer occasions; "occasional": encountered on fewer than half of collecting trips; "frequent": encountered in low numbers on most collecting trips; "common": encountered on almost all collecting trips, often with several individuals; "superabundant": encountered on almost every slab.

 

Group

Taxon

Notes

Trilobites

Ogyginus corndensis

Common, including as complete juveniles

 

Ogygiacarella debuchii

Moderately common

 

Cnemidopyge parva

Occasional complete moults

 

Protolloydolithus reticulatus

Occasional

 

Platycalymene simulata

Rare – one complete meraspis

 

Rorringtonia kennedyi

Occasional

 

Geragnostus mccoyii

Occasional

 

odontopleurid indet.

Rare – one rib fragment

 

Microparia lusca

Rare – few near-complete adults

 

Other cyclopygids (indet.)

Rare fragments

 

Barrandia cordai

Rare

Brachiopods

Apatobolus? micula

Superabundant

 

Palaeoglossa attentuata

Common

 

Monobolina ramsayi

Occasional

 

Opsiconidion nudum

Occasional

 

Schizocrania cf. salopiensis

Occasional–only encrusting undetermined substrate

 

Meristopacha granulata?

Rare

 

Dalmanellid indet.

Rare

Graptolites

Cryptograptus tricornis

Frequent

 

Hustedograptus? teretiusculus

Occasional

 

Dendrograptus spp.

Rare; at least two species

Echinoderms

Cystoid indet.

Rare – one specimen and one possible

 

Anatifopsis? sp.

Common

 

Galliaecystis? sp.

Rare – fragments of four specimens

 

Solute undet.

Rare – one articulated specimen

 

Carpoid indet.

Rare – one specimen

 

Oesolcucumaria eostre gen. et sp. nov.

Occasional

Cnidarians

Sphenothallus sp.

rare – few specimens

 

Conulariid indet.

Rare – one specimen

Ostracodes

Undetermined smooth form

Common

 

Bullaeferum sp.

Occasional

 

Nanopsis sp.

Occasional

Chordates

Conodonts

Occasional as isolated elements; rare as clusters (pellets?)

Molluscs

Bivalve indet

Rare

 

Gastropod indet.

Rare – few specimens

 

Nautiloids indet.

Rare – few specimens

Sponges

Pirania? sp.

Rare

 

Wapkia-like form

Occasional

 

Xylochos? sp.

Occasional

 

Reticulosan sp. 1

Frequent

 

Reticulosan sp. 2

Frequent

 

Hexactinellid indet.

Rare

 

Sponges undet. (several spp.)

Rare

 

Eiffeliid indet.

Isolated spicules only

Worms

Palaeoscolecid gen. et sp. nov. (Botting et al. in press)

One confirmed specimen; many too poorly preserved to identify

 

Palaeoscolecid undet.

One specimen with different plating to Palaeoscolecid gen. et sp. nov.

 

Scolecodonts

One associated pair of elements

Undet.

Algal remains?

Remains on which ostracodes are feeding

 

TABLE 2. Approximate proportions of the fauna in terms of collected and life abundance, based on largely non-analytical collecting over 10 years; the figures are therefore not rigorous, but instead estimated values from our observations. The correction factor is based on the ratio of articulated to fragmented scleritomes of Anatifopsis?, representing the proportion of individuals affected by rapid burial, which was then applied to other multi-element scleritomes. Deviations from this factor were employed to allow for ecdysis and additional requirements of soft-tissue preservation; see text for more details.

 

 

complete (c)

disarticulated

(d)

Correction
factor (Ci)

Estimated relative
life abundance = c(Ci+1)

Apatobolus? micula

>100

Many

 

>>1000

sponges

50

Not visible

20

1050

palaeoscolecids

17

2 fragments

~20

357

trilobites

10 (non-moult)

50 (moults)

?

20

20/5=4

<210

<250

ostracodes

30

Many

20/4=5

180

holothurians

8

Not visible

20+

>168

mitrates

7

~140

20

~147

other brachiopods

?

100

-

100

graptolites

80

n/a

-

80

solutes

1

Not visible

20

21

bivalves

5

n/a

-

5

cornutes

0

4

-

4

nautiloids

3

n/a

-

3

sphenothallids

3

n/a

-

3

gastropods

2

n/a

-

2

TABLE 3. Expected taxonomic composition of the preserved fauna under different degrees of preservation. "Poor preservation" implies an entirely disarticulated and washed assemblage of shelly fragments. "Moderate preservation" implies a fauna lacking abrupt burial and soft tissue, but without extended sea-floor exposure or winnowing. The observed fauna is extensive, but will inevitably be increased by further collecting, as taxa from the tail of the hollow curve are discovered. The total diversity of macrobiota in the local area at the time of deposition is impossible to ascertain, but it was likely to have been in excess of 100 species, by comparison with major Lagerstätten such as the Fezouata Biota (Van Roy et al., 2010) and the Burgess Shale (Conway Morris, 1986). In these deposits, many taxa are localised, and were found only after extensive collecting.

 

Complete biota

Holothurian Bed

Moderate preservation

Poor preservation

Trilobites (?11 spp)

Trilobites (11 spp)

Trilobites (11 spp)

Trilobites (<11 spp, frag.)

Brachiopods (?7 spp)

Brachiopods (7 spp)

Brachiopods (7 spp)

Brachiopods (?7 spp)

Other shelly taxa (?8 spp)

Other shelly taxa (8 spp)

Other shelly taxa (8 spp)

Other shelly taxa (<8 spp)

Graptolites (?5 spp)

Graptolites (5 spp)

Graptolites (5 spp)

Graptolites (?5 spp)

Sponges (? 10 spp)

Sponges (10 spp)

Sponges (spicules only)

Sponges (spicules only)

Conodonts (?1 sp.)

Conodonts (1 sp.)

Conodonts (1 sp.)

Conodonts (1 sp.)

Carpoids etc. (?3 spp)

Carpoids ( 3 spp)

Carpoids (2 spp)

Anatifopsis? plates only

Cystoids (?1 sp.)

Cystoids (1 sp.)

-

-

Algae (?1 sp.)

Algae? (1 sp.)

-

-

Holothurians (?1 sp.)

Holothurians (1 sp.)

-

-

Palaeoscolecidans (?2 spp)

Palaeoscolecidans (2 spp)

-

-

Unmineralised arthropods

-

-

-

Unmineralised worms

-

-

-

Other soft-bodied taxa

-

-

-

Estimated total: ?

51

35

<30