ID Keys

*Images in development

Anomalodesmata

#1

Shells markedy inequivalve, one flat one concave

Shells equivalve or slightly inequivalve but one valve is never flat

#2

Posterior dorsal margin concave

Pandora inaequivalvis

Posterior dorsal margin straight

#3

Ligament set on a on a deeply sunken resilifer, visible externally but may be very small

Ligament set on an internal chondrophore or wholly internal resilifer, not visible externally

#4

Shell nacreous, subovate to trigonal wedge-shaped with weak radial ridges and/or minute pustules or prickles arranged in radial rows

Shell chalky, subovate to oblong, lacking radial ridges, surface may be granular, but not arranged into radial rows

#5

Shell wedge shaped, very broad anteriorly with weak radial ribs and microscopic prickles arranged in rows

Shell ovate to subspherical, lacking radial ribs but with microscopic radially arranged pustules

#6

Shell subspherical, strongly umbonate, posterior rounded

Cetomya tornata

Shell subovate, posterior subtruncate

#7

Internal ligament in a brooad shallow chondrophore, external ligament small, cardinal tooth in RV, pustules easily visible

Poromya granulata

Ligament wholly external, set in a shallow sunken resilifer, lacking teeth, pustules microscopic best seen at margins

Cetoconcha bulla

#8

Beaks in front of midline, oval to oblong often mis-shapen

Thracia distorta

Beaks at or behind the midline

#9

Outline subovate to subtrigonal (H≈L)

Outline oblong (L>H)

#10

Outline subtrigonal, umbonate, narrowed posterior set off by a weak ridge, shell smooth

Thracia convexa

Outline subovate, posterior dorsal margin concave, shell with granular micro-sculpture

Thracia myopsis

#11

Pallial sinus shallow, wide extending to only half way to point under resilifer

Thracia pubescens

Pallial sinus deep, rounded extending to point beneath the resilifer

#12

Posterior area set off by a distinct angulation, posterior margin truncate, posterior area more coarsely granular than remainder

Posterior area weakly defined, posterior margin rounded subtruncate coarse granulation over whole of shell

Thracia villosiuscula

#13

Posterior granulation coarse

Thracia gracilis

Posterior granulation fine

Thracia phaseolina

#14

Chondrophore tooth-like extending into umbonal cavity, umbos with a small stress fracture

Chondrophore shallow or absent then ligament supported by lithodesma only

#15

Oblong shell, beaks behind midline, posterior narrowed, with granular microsculpture

Cochlodesma praetenue

Subovate-trigonal, fragile, hyaline (lower slope, abyssal)

Cochlodesma tenerum

#16

Elongate oval to oblong shells, beaks at midline

Subcircular to quadrate shells with beaks at midline or subquadrate shells with beaks in front of midline

#17

Elongate ovate, posterior truncate, overall with fine radial raised lines and with agglutinated sediment grains especially on the posterior area

Lyonsia norwegica

Oblong, posterior obliquely truncate, posterior area set off by an oblique ridge, posterior area with radial riblets, anterior area with weak oblique ridges, overall with microscopic spines in radial rows

Allogramma formosa

#18

Subcircular shell with coiled beaks and 13-16 acute carinate radial ribs

Spinosipella acuticostata

Subovate to quadrate shells lacking prominent radial ribs

#19

Quadrate-polygonal solid shell with a median oblique carina and a lower carina on either side dividing shell into 4 regions

Halicardia flexuosa

Shell not massive or divided into regions by carinae

#20

Shell triangular to subquadrate overall with microscopic pustules

Shells quadrate with fine radial raised lines

#21

Shell triangular, beaks at midline, pustules arranged in rows

Verticordia triangularis

Shell obliquely oval or subquadrate

#22

Shell subquadrate, posterior truncate, weak radial lines present

Lyonsiella abyssicola

Shell subovate, posterior rounded, radial lines absent, pustules large

Lyonsiella subquadrata

#23

Posterior dorsal margin sloping creating a broadly rounded anterior margin and somewhat extended ventrally, radial line dense up to 50 in largest

Policordia densicostata

Posterior dorsal margin straight creating a narrowly rounded anterior profile. Similar shells from the subarctic and arctic are referred to Policordia jeffreysi. Policordia atlantica has a sculpture of sunken grooves rather than raised threads and is not recorded from the NE Atlantic.

Policordia gemma