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Identify your eggcase

Glossary:

Capsule: Central capsule of the eggcase, within which the embryo develops.
Capsule size: Given by length and width ranges based on data submitted to the Shark Trust. Capsule length includes both fields but excludes the horns. Capsule width includes the lateral keels.
Concave: Curves/dips inwards.
Convex: Curves/dips outwards.
Distal: Bottom end of capsule.

Proximal: Top end of capsule where juvenile exits.
Fields: Flattened extensions at either end of the capsule, between the horns.

Keels: Flattened extensions running along either side of the capsule.
Filamentous: Strap-like, like shoe-laces.
Longitudinal: Along the length of the structure.

Download Eggcase ID Guide

(Print friendly version)

Download the Eggcase ID Key

(A printable version of the one below)

Eggcase Identification Key

Unsoaked and soaked common skate eggcases - note the soaked eggcase is almost double the size of the unsoaked

Please Note!

All eggcase sizes relate to soaked eggcases. (Eggcases expand considerably when soaked - Look at the example on the right!)

All sizes are approximate and as our data set increases in size more accurate sizes will be elucidated

1a

Eggcase is goblet shaped with very curly tendrils? Go to 2

Bull huss eggcase

1b

Eggcase is flattened, more square in shape and, if they are not broken, will have horns on each of it’s four corners. Go to 3

2a

Eggcase is greater than 6 cm in length. Scyliorhinus stellaris: Nursehound, Bull Huss.

2b

Eggcase is shorter than 6 cm. Scyliorhinus canicula: Lesser Spotted Catshark, “dogfish”.

3a

Keels are present on the eggcase. Go to 4

Eggcase keel

3b

There are no keels present. Go to 9

Eggcase - no keels

4a

Eggcase capsule length is greater than 16 cm. Go to 5

4b

Capsule length less than 16 cm. Go to 6

5a

Proximal field long and usually ragged. Dipturus batis: Common Skate.

5b

Proximal field small and neat. Rostroraja alba: White Skate.

6a

Eggcase has “washboard” texture on one side of the capsule body: Amblyraja radiata: Starry Skate.

6b

Capsule body is smooth (striations may or may not be present and should not be confused with the “washboard” texture). Go to 7

7a

Capsule tapers (from proximal to distal) – if proximal horns are present they are long and filamentous, distal horns are short and hooked. Raja microocellata: Small-eyed Ray.

7b

Capsule is square/rectangular in shape. Go to 8

8a Eggcase (including horns) almost fills an adult's hand. Raja brachyura: Blonde Ray.

8b Eggcase (including horns) fills an adult's palm. Raja clavata: Thornback Ray.

9a Eggcase is small, neat and well rounded in the capsule. If horns are present they are very long and curved inwards. Leucoraja naevus: Cuckoo Ray.

9b Eggcase is stouter, larger and less rounded in its appearance. Go to 10

10a Eggcase found within the red area on the distribution map. (Map demonstrates a broad deliniation and there is a certain degree of crossover at the fringes. If you are uncertain, go to 11). Go to 11 Undulate ray distribution map

10b Eggcase found within of the red area on the distribution map. (Map demonstrates a broad deliniation and there is a certain degree of crossover at the fringes. If you are uncertain, go to 11). Raja montagui: Spotted Ray. Spotted ray distribution

11a Eggcase is, generally, larger (see 11b) has rough edges on the keels and the proximal horns splay outwards from the capsule. Raja undulata: Undulate Ray.

11b Eggcase is, generally, smaller with defined keel edges. Proximal horns extend away from the body in a parallel line. Raja montagui: Spotted Ray.

Identification

Eggcase Morphology

ID Guide

International Eggcases

Species