Animal and animal produce inspired signs

Animal and animal produce inspired signs may sound a little silly, but the radiology literature is replete with such signs, some more fanciful than others.

Fish and seafood

• cluster of black pearls sign
• endosteal scalloping: medullary cavity masses, e.g. multiple myeloma
• fish vertebra (also known as codfish vertebra): biconcave vertebrae as seen in osteoporosis
• fishtail deformity of the elbow: due to abnormal trochlear ossification following a distal humeral fracture in childhood 
• lobster claw sign of papillary necrosis
• manta ray sign of bladder exstrophy
• vertebral scalloping: may be anterior or posterior border

Birds

• bird-beak sign of achalasia (also known as rat tail sign)
• beak sign of arterial dissection or of sigmoid volvulus
• eggshell calcification of silicosis and occasionally sarcoidosis
• gull wing appearance of erosive osteoarthritis
• hummingbird sign or penguin sign
• owl-eyes sign of anterior spinal cord infarction etc... 
• swan neck deformity of rheumatoid arthritis
• winking owl sign

Mammals

• anteater nose sign of calcaneonavicular coalition
• bat's wing
  • pulmonary opacities, e.g. in alveolar oedema
  • 4^th ventricle (Joubert anomaly and related syndromes)
• bear's paw sign: xanthogranulomatous pyelonephritis
• beaver tail liver
• buffalo chest: bilateral pneumothoraces due to abnormal communication between the pleural spaces
• bull's eye: evoked in the mind's eye by many a pathology
• dog ear sign: fluid/blood in pelvic peritoneal recess
• dural tail: of meningioma and several other dura-based lesions
• eye of tiger sign: classical of Hallervorden-Spatz syndrome
• feline oesophagus: horizontal striations seen on barium swallows as a variant of normal
• hidebound sign of gastrointestinal scleroderma
• joint mouse: intra-articular loose body resulting from osteochondritisdissecans
• leather bottle stomach: of linitis plastica
• leopard skin sign or tigroid pattern
• moose head appearance of corpus callosal dysgenesis
• panda sign
  • of the midbrain in Wilson disease
  • of sarcoidosis
• piglet sign of osmotic demyelination
• pleural mouse
• raccoon eyes sign
• rat bite erosions of gout
• rat tail sign of arterial dissection or of achalasia (also known as bird-beak sign)
• Scottie dog sign
• staghorn calculus: struvite renal calculi
• tigroid pattern or leopard skin sign

Insects

• butterfly fracture
• butterfly glioma: glioma crossing midline to the contralateral hemisphere
• butterfly shape of the grey matter of the spinal cord
• butterfly vertebra
• caterpillar sign: of pyloric stenosis

Reptiles

• cobra head sign of ureterocele
• snake-eye appearance: pathology of anterior horns of cervical grey matter
• snake eyes
  • appearance of the facial canal in the petrous temporal bone
  • alternative name for owl-eyes sign of spinal cord infarction
• snake sign (or serpent sign)

Micro-organisms

• plankton sign: diagnostic on ultrasound of an exudative pleural effusion

Mythical creatures

• cyclops lesion: usually post-ACL repair
• medusa head
  • of a developmental venous anomaly (DVA) 
  • also a sign of severe portal hypertension (i.e. caput medusae)

Animal product foods

• cervical hamburger sign: normal cervical facet joints on axial CT
• cluster of black pearls sign
• head cheese sign of hypersensitivity pneumonitis
• honeycomb lung of UIP/pulmonary fibrosis
• ice cream cone sign of acoustic neuroma
• leather bottle stomach: of linitis plastica
• mesenteric hamburger sign (also called sandwich sign): mesenteric nodal mass
• omental cake: metastases to omentum
• sausage digit: underlying inflammatory arthritis or dactylitis
• water bottle sign: massive pericardial effusion