Field Guide to Malformations 

of Frogs and Toads 

With Radiographic Interpretations

U.S. Department of the Interior,

U.S. Geological Survey

Biological Science Report 

USGS/BRD/BSR–2000–0005
Acknowledgments

This field guide began as part of The Amphibian Health

Examinations and Disease Monitoring workshop coordinated

by U.S. Fish and Wildlife Service National Conservation

Training Center (NCTC) in February 2000. The

malformations presented here are not intended to be an

exhaustive summary of all potential types of malformations.

These malformations represent the major types of

malformations found in approximately 200 recently

metamorphosed frogs that were collected in Minnesota,

Vermont, Wisconsin and Maine and examined at the

USGS–National Wildlife Health Center in Madison,

Wisconsin (NWHC). These studies focused on the northern

leopard frog (Rana pipiens). The malformations and the

method of their classification are reported in much greater

detail in the publications from which this information was

excerpted (Meteyer, C.U., et al., 2000). 

Jewel Bennett, Karene Motivans, and Kelly Fike, NCTC,

provided the final design, production and printing of the field

guide. Denim Jochimsen and Harry Rihn, NWHC, provided

assistance with the initial draft of the guide. Information on

more training available through NCTC can be obtained at the

NCTC homepage www.nctc.fws.gov. 

Frogs in this field guide were collected during 1997–1998

survey efforts conducted in Minnesota by Judy C. Helgen,

Dorothy Bower, and Susan Kersten, Minnesota Pollution

Control Agency; Vermont by Richard Levey, Vermont Agency

of Natural Resources, and Laura Eaton–Poole, U.S. Fish and

Wildlife Service Ecological Services; and Maine by Kathryn A.

Converse, NWHC. The technical staff of the NWHC Lab

Investigations Branch provided photography, radiography, and

necropsy support.

Scientific Review of this guide was provided by Dr. Doug

Johnson, Dr. Doug Campbell, Dr. Ian Barker, Dr. D. Earl

Green, Jeff Canfield, and Dottie Johnson.

Reporting Malformations

Malformations can be reported to the North American

Reporting Center for Amphibian Malformations (NARCAM)

on their website at www.npwrc.usgs.gov/ narcam, or by

phoning 1 800/238 9801. For results from more extensive

surveys, information can also be submitted via mail by

sending a spreadsheet or disk with the information on it to

NARCAM, Northern Prairie Wildlife Research Center, 8711

37th St. SE, Jamestown, ND 58401. Basic information

reported to NARCAM should include the date, species,

numbers of both normal and malformed amphibians

encountered, and a description of the malformation, along

with the location of the malformation, including the state,

county, and specific site.

Obtaining More Copies

Copies of the field guide may be obtained through:

Publications Clearinghouse at NCTC at www.nctc.fws.gov/

library/pubunit.html, or by calling 800/344 WILD, or the

NWHC web site www.umesc.usgs.gov/http_data/nwhc/frog/

frogmalf.html. 
Field Guide to

Malformations 

of Frogs and Toads 

With Radiographic Interpretations

Carol U. Meteyer 

USGS National Wildlife Health Center

Madison, WI 53711 

608/270 2462

http://www.emtc.usgs.gov/nwhchome.html

Funding for this project was provided in part by the USGS Biological Resource

Division Eastern Region; the Northern Prairie Wildlife Research Center

Grasslands Ecosystem Initiative; the National Institute for Environmental

Health Science, Environmental Toxicology Program and U.S. Fish and Wildlife

Service, National Conservation Training Center.

Suggested citation: Meteyer, C.U. 2000. Field guide to malformations of frogs

and toads with radiographic interpretations. Biological Science Report

USGS/BRD/BSR–2000–0005

Cover photo by: Ryan Hagerty
2

In 1995, students found numerous

malformed frogs on a field trip to a

Minnesota pond. Since that time,

reports of malformed frogs have

increased dramatically. Malformed

frogs have now been reported in 44

states in 38 species of frogs, and 19

species of toads. Estimates as high as

60% of the newly metamorphosed

frog populations have had

malformations at some ponds

(NARCAM, ’99). The wide geographic

distribution of malformed frogs and

the variety of malformations are a

concern to resource managers,

research scientists and public health

officials. The potential for

malformations to serve as a signal of

ecosystem disruption, and the affect

this potential disruption might have

on other organisms that share those

ecosystems, has not been resolved.

Malformations represent an error

that occurred early in development.

The event that caused the

developmental error is temporally

distant from the malformation we see

in the fully developed animal.

Knowledge of normal developmental

principles is necessary to design

thoughtful investigations that will

define the events involved in abnormal

development in wild frog populations. 

Development begins at the time an

egg is fertilized and progresses by

chemical communication between cells

and cell layers. This communication is

programmed through gene

expression. Malformations represent

primary errors in development,

errors in chemical communication or

translation of genetic information.

Deformations arise later in

development and usually result from

the influence of mechanical factors

(such as amputation) that alter shape

or anatomy of a structure that has

developed normally. The occurrence

and the type of malformations are

influenced by the type of error or

insult as well as the timing of the

error (the developmental stage at

which the error occurred). The

appearance of the malformation can

therefore provide clues that suggest

when the error may have occurred.

If the malformation is an incomplete

organ, such as an incomplete limb, the

Introduction

factor or insult acted during a

susceptible period prior to organ

completion (Robbins S.L., et al.,

1984). Although defining the

anatomy of the malformed

metamorphosed frog can give us an

idea of the approximate window

during which the developmental

insult was initiated, and might even

suggest the type of insult that may

have occurred, the morphology of

the malformation does not define

the cause. To define causes and

mechanisms of frog malformations

we need to use well designed

investigations that are different from

traditional tests used in acute toxicity

or disease pathogenicity studies.

When investigating malformations

in metamorphosed frogs, we are

looking at the affect of exposure to an

agent that occurred early in tadpole

development. Therefore

investigations to determine causes of

malformations need to look at agents

that are present in the tadpoles or

their environments at these early

developmental times. Laboratory

experiments need to expose

embryos and tadpoles to suspect

agents at appropriate developmental

stages and look at acute results,

such as toxicity and death, as well

as following the developmental

process to completion to determine

the impact of the agent on the

developing tadpole and the fully

developed frog. This means holding

animals past metamorphic climax 

to assure that the anatomy and

physiology of the adult have

developed normally. 

As we look at field collections of

abnormal frogs, we need to keep in

mind that these collections reflect

survivors only. We are looking at

malformations that were not fatal 

to tadpoles. We cannot assume that

because we do not collect other

malformations, they did not exist.

More work needs to be done on the

developing tadpole, in the field and in

the laboratory, to better elucidate the

range, frequency, character and

causes of anuran malformations. 

Pickerel frog

USFWS Photo by: G. Atwell

American toad

USFWS Photo by: K. Hollingsworth

Northern Leopard frog

USFWS Photo by: J. Rorabaugh
3

Descriptions of frog malformations in

this report are based on terminology

used in human literature (Bolande,

1979; Robbins, et al., 1989),

developmental biology (O’Rahilly, et al.,

1996; Carlson, 1994; Gilbert, 1997), and

teratology (Wise, et al., 1997). Many of

these terms were originally used to

describe abnormalities in the

mammalian fetus at birth. However,

application of common terminology

may allow comparison of similar

conditions in related specialties and

across species and bring new interest

and collaboration to the issues

involving malformed frogs and toads. 

Amelia: No evidence of a limb, the hip

region is smooth and the pigment

pattern is not disrupted.

Anophthalmia: Missing eye.

Aplasia (agenesis): Lack of development

of an organ or tissue often resulting

from failure of appearance of the

primordium of an organ in embryonic

development. For example, amelia is

aplasia or agenesis of a limb.

Brachydactyly: Short toe; The normal

number of metatarsal bones are

present but the number of phalanges

(bones in the toe) are reduced.

Brachygnathia: Abnormal shortness 

of lower jaw; same as mandibular

micrognathia.

Bilaterally symmetrical rear limb

malformations refer to the occurrence of

the same type of malformation in both

rear limbs.

Bilateral rear limb malformations refer to

the occurrence of malformations of any

type in both rear limbs.

Bone bridge: A bone structure that

spans the space between two margins

of bent bone. This bone structure

appears radiographically as a plane of

linear rays of bone that extend from the

margins of bent bone and fill the angle

between the bone margins.

Complete but malformed limb: All bones

of the limb are present, but the limb is

still abnormal e.g., rotation, bone

bridge, skin web, micromelia.

Deformations: Deformations arise later

in fetal life and represent alterations 

in form or structure resulting from

mechanical factors such as amputation.

A deformation does not involve an

intrinsic defect in morphogenesis and

impacts a structure that otherwise

developed normally. 

Digits: Toes; identified by the number of

phalanges and relative position on the

foot or hand (Fig. 1C page 4).

Ectoderm: The embryonic layer from

which epidermal tissues (skin, hair,

etc.), mucous membranes, nervous

tissue, and external sense organs 

(eye, ear, etc.) are derived. 

Ectrodactyly: Missing toe; Distinguished

from brachydactyly and refers to a

completely missing digit including 

the metatarsal bone and phalanges.

Ectromelia: An incomplete limb with the

lower portion of the leg missing. Types

of ectromelia refer to the last

identifiable bone e.g., ectromelia of the

femur, ectromelia of the tibiafibula, and

ectromelia of the tibiale and fibulare.

Phocomelia and amelia are also

considered types of ectromelia.

Hemimelia: Short bone; The affected

bone is short but distal limb and foot

are present, e.g., hemimelia of the

tibiafibula, means the tibiafibula is

short but the foot is present.

Hypoplasia: Incomplete development 

of an organ.

Hock joint: Ankle.

Kyphosis: Abnormally convex

(hunchback) thoracic spine.

Malformations: Primary errors in any

phase of morphogenesis including cell

proliferation, cell migration,

differentiation, programmed cell death

or regression of larval structures. 

Mesoderm: The embryonic layer from

which connective tissue, bone, cartilage,

muscle, blood, vasculature, notochord,

pleura, pericardium, peritoneum,

kidney, and gonads are derived.

Microcephaly: Small head, blunt snout.

Micromelia: Proportionaly small or

short limb.

Microphthalmia: Small eye.

Morphogenesis: The development 

of highly organized and specialized

tissues through cell division and

proliferation, cell migration, cell

differentiation, and programmed cell

death all of which are orchestrated

through chemical communication within

and between cells.

Pathogenesis: Cellular events and tissue

reactions that occur in the progression

of disease.

Phocomelia: Absence of the proximal

portion of a limb, with the foot attached

very close to the body and proximal

bones that cannot be identified.

Phalanges: Bones of the toe.

Polydactyly: More than the normal

number of metatarsal bones are

present with or without a complete set

of phalanges.

Polymelia: More than two forelimbs or

more than two rear limbs are present.

The extra limb needs to have

identifiable major segments (e.g. femur

and tibiafibula) to be classified as a

multiple limb. 

Polyphalangy: The normal number of

metatarsal bones are present at the

tibiale-fibulare-metatarsal joint but

with duplicate sets of phalanges. 

Rotation: Distortion of the direction of

bone growth in such a way that the

orientation of the limb and foot is

abnormal. Primary rotation is the

misdirection of bone growth without a

predisposing cause such as a fracture, a

bone bridge or a skin web. A secondary

rotation also has abnormal orientation

of the foot, but it is due to the formation

of a bone bridge, skin web or fracture.

Scoliosis: Lateral deviation (either left

or right) in the normally straight line of

the spine.

Skin web: A band of skin crossing 

a joint and restricting motion 

of that limb. 

Stifle joint: Knee.

Teratogen: An agent or factor that

causes malformations.

Teratogenesis: Abnormal development

that gives rise to malformations

Glossary
4

Diagram is adapted from Duellman, et al., 1996.

I. No limb

A. Amelia 2A–B

II. Reduced limb segments

A. Ectromelia 2C–F, 3A–D

B. Phocomelia 3E–F

General Classification System 

for Limb Malformations

III.Complete but malformed limb

A. Skin web 4A–B

B. Bone bridge 4C–D

C. Rotation 4E–F, 5A–D, 6A–F

D. Hemimelia 5C–D, 6A–F

E. Micromelia 5E

IV. Reduced limb elements

A. Ectrodactyly

B. Brachydactyly 5C–D

C. Brachydactyly with

Ectrodacytly 6A–F

Limb Elements 

femur 

tibiafibula 

tibiale

fibulare 

digits 

metatarsal phalanges bones 

ilium

coccyx 

acetabulum

ischium 

1 2 3 4 

5

Anatomy and

terminology

describing the

normal frog limb. 

1A

1B 1C

V. Multiple limb elements

A. Polydactyly

B. Polyphalangy 7A–F

C. Polydactyly and

Polyphalangy 8A–B

VI.Multiple limb segments

A. Polymelia 8C–F, 9A–E
5

Amelia

No bone has developed beyond the pelvis and the contour over the right hip is smooth. Displacement of the

coccyx gives the appearance of scoliosis (curve to the right) although the vertebrae are properly aligned. The

pelvis is usually abnormal in frogs with amelia. The frog in the images above is missing the right ilium.

Ectromelia of the femur

The femur is present but ends mid shaft. There is no evidence of a stifle (knee) joint.

Bilateral ectromelia of the femur 

The right femur is very short and difficult to discern, but

as long as there is any bulge at the hip it can be assumed

that a portion of the femur is present. Movement of the

partial femur can often be seen under the skin.

2A 2B

2C 2D

2E 2F

Ectromelia of the femur with pigment malformation of the limb

Note the abnormal small reticular pattern of brownblack pigment over the right limb rather than the large

spots of black-brown pigment which are normal for the

leopard frog. At present, this is considered a malformation

of skin pigment pattern. The melanophores that contain

pigment are of ectodermal (neural crest) origin, and

might be another form of inappropriate pattern

determination in the malformation syndrome.
Ectromelia of the tibiafibula

As long as the stifle (knee) is present, a portion of the tibiafibula must be present. In this frog, although the

right tibiafibula is hard to identify without radiographs, we know that a portion of the bone must be there

because the stifle is well defined.

Ectromelia of the tibiale and fibulare

The left hock (ankle) joint is present, indicating that the tibiale and fibulare are present. The tibiale and

fibulare are incomplete, however, and the digits are absent.

Phocomelia

The right limb is very short with no distinct femur or tibiafibula. This is phocomelia and not ectromelia because

a foot is present. This foot is very abnormal with only four metatarsal bones (ectrodactyly) associated with four

terminal phalanges (brachydactyly).

6

3A 3B

3C 3D

3E 3F
7

Bilateral skin webbing 

Continuous bands of skin connect the hip to the hock. These webs of skin can be of various length and “tightness” but

must cross a joint (usually stifle) to be a skin web. Skin webs are bilateral in frog (4A) and unilateral (left side) in frog (4B).

Bone bridge of the femur

Bone bridging is difficult to discern in the live frog. The primary clues are a short, thick, bent long bone which

may be palpable as a wide solid bone beneath the skin. Although skin webbing may be present with bone

bridging, the skin web would again need to cross the stifle joint and not just “cover” a thickened bone.

Radiographs show that these bone bridges form delicate rays of bone along the margins of bent long bone. Bone

bridges may occur in any of the long bones including femur, tibiafibula and the tibiale and fibulare.

Bone bridge of the tibiafibula and “secondary” limb rotation

The left tibiafibula bends sharply at mid shaft and a bone bridge spans the angle of this bend. The tibiale and

fibulare are short but the digits are relatively unremarkable. Although rotation is present, it is secondary to the

bone bridge.

4A 4B

4C 4D

4E 4F
8

Bilateral primary rotation

To classify a limb as a primary rotation, there should be no associated bone bridging or skin webbing. The distortion 

in these limbs is from intermittent bends in the long bones. This malformation is usually bilateral.

Micromelia

The right limb has all of its bones, but they are short

with poorly developed muscle. The joints of these

short limbs can be fused and immobile. This frog is

also missing the right eye.

Brachydactyly, hemimelia of tibiafibula, and rotation

Five digits (five metatarsal bones) are present but short, indicating missing phalanges (brachydactyly). Radiographs

show the number of phalanges in the digits (medial to lateral) are 1, 3, 2, 2, 0. The tibiafibula is short, thick and

rotated approximately 180 degrees because the longest toe (digit 4) is second from the midline suggesting a reversed

digit order of 5, 4, 3, 2, 1. This is not phocomelia because a femur is present.

5A 5B

5E

5C 5D
Ectrodactyly, brachydactyly, hemimelia of tibiafibula, and rotation

The tibiafibula is short, thick and rotated. However, this is not ectromelia of the tibiafibula because digits are

present. The three digits (ectrodactyly) are very abnormal and short (brachydactyly). Although it cannot be

seen in the live specimen, the tibiale and fibulare are absent.

Left limb: Bone bridge, hemimelia of tibiafibula, rotation, ectrodactyly and brachydactyly 

The tibiafibula is short, bent and a bone bridge fills the broad angle of the bend. There are four (ectrodactyly) short

(brachydactyly) digits. The longest digit is in the second position suggesting 180 degrees rotation with digit order of

5,4,3,2,1. This is not skin webbing (skin does not cross a joint), the skin simply covers a very thick bone bridge.

Right limb: Rotation, ectrodactyly and brachydactyly 

Only four digits are present (ectrodactyly) and all are short (brachydactyly). The distal tibiafibula is thick and

rotated. The tibiale and fibulare are very small oval bones.

Left limb: Bone bridge, hemimelia of tibiafibula, skin web, rotation, ectrodactyly and brachydactyly 

The tibiafibula is short, bent, and rotated. The bend is traversed by a bone bridge. A short skin web crosses the

stifle. The tibiale or fibulare is missing and the remaining bone is short. Only three digits are present (ectrodactyly)

and they are all short (brachydactyly).

Right limb: Ectrodactyly and brachydactyly 

The tibiale and fibulare are rotated. There are only three digits (ectrodactyly) and they are all short (brachydactyly).

9

6A 6B

6C 6D

6E 6F
Ectrodactyly, brachydactyly, polyphalangy

The left foot has only two digits (ectrodactyly) and they are both short (brachydactyly). The right foot has four digits

with 1, 2, 2, 1 phalanges respectively. The last phalanx of the longest digit on the right foot is duplicated (polyphalangy).

Ectrodactyly, brachydactyly, polyphalangy with an unusual bone bridge

The left limb has a triangular–shaped tibiale-fibulare region, which is actually a long curved fibulare and a very

short tibiale. This is not a skin web because it simply covers a bone structure and does not traverse a joint. Only

three digits are present (ectrodactyly) and they are short (brachydactyly). The first phalanx of the longest digit

splits and articulates with two terminal phalanges (polyphalangy).

Bone bridge, polyphalangy, and brachydactyly

The tibiafibula is folded on itself and the folded bone creates a bone bridge. The tibiale and fibulare are

unremarkable. Eight digits can be counted but the left foot has a normal number of metatarsal bones. Metatarsal

bones 4 and 5 are split midshaft resulting in polyphalangy. Digit 3 has duplication of the first phalanx at the

metatarsal phalangeal joint, also resulting in polyphalangy. Two of the duplicated digits are short (brachydactyly).

10

7A 7B

7C 7D

7E 7F
Polydactyly and polyphalangy

There are eight digits (polydactyly), which are poorly separated in the image of the live frog. The radiograph

shows digits as 1, 2, 3, 4 (3 or 5), 3, 4, 5. The long digit second from the mid line (digit 4) has a duplicated last

phalanx (polyphalangy).

Polymelia

The femur and tibiafibula are duplicated, therefore the classification is polymelia. The multiple femurs were not

seen in this live specimen but the thickened bone at the end of the femur and stifle were palpable. A duplicate

limb that becomes obvious at the stifle suggests that a portion of the femur is also duplicated.

Polymelia

The fused femurs originate at multiple pelvic elements. The two duplicated limbs are present as “mirror

images” of each other.

11

8A 8B

8C 8D

8E 8F
12

Polymelia

Although the multiple right limbs do not appear separated in the live specimen, the entire limb is very wide and

there are 12 toes. This provides good evidence that the bones of the limb are duplicated. The radiograph shows

two right femurs, five tibia/fibula bones and five tibiale/fibulare bones.

Muliple forelimbs

This bronze frog has almost identical and easily

recognizable multiple forelimbs.

Muliple forelimbs

This bullfrog has a mass of multiple limbs.

Photo by Dr. R.R. Dubielzig

9A 9B

9C 9D

9E

Small bone projections

This late-stage tadpole has an abnormal structure

projecting from the region of the tibiafibula. This is

not a multiple limb because no joint or identifiable

segments are present.

9F

Muliple forelimbs

The forelimbs of ranids do not emerge until

metamorphosis and multiple forelimbs can remain

under the skin.
13

Microcephaly 

The frogs on the far left and far right(10A, 10D) have small heads and their snout is blunt and curved. The heads of

the frogs in the center (10B, 10C) are normal.

10E 10F 10G 10H

Eye abnormalities

10E Normal eye in a frog.

10F Small left eye in a frog (microphthalmia).

10G Frog missing left eye (anophthalmia).

10H The left eye has no iris and therefore appears uniformly black.

10I Tadpole missing right eye (anophthalmia).

10J 10K 10L

Brachygnathia (mandibular micrognathia)

The first frog (10J) has a normal jaw with uniform closure of the margins of the mouth. The second frog (10K) has a

short lower jaw (mild brachygnathia) that is curved to the left. The third frog (10L) has a severely distorted jaw with

an irregular margin that does not meet the margins of the upper jaw (severe brachygnathia) leaving a large open gap

that makes closure impossible.

10A 10B 10C 10D

10I 
14

Not all irregular contours on the frog are malformations. 

These frogs have a mass on the left side of their backs (arrows). When submerged in water, a pore opens and 

fly larvae (maggots) can be seen beneath the skin. Figure 11B is an enlargement of the area at the point of the

yellow arrow in 11A.

Trauma–Limb amputation

The terminal margin of the right femur is blunt,

irregular, red and swollen indicating trauma.

Hemorrhage can be seen along the cut surface.

Abnormalities, Not Malformations

11A 11B

11C 11D

Trauma–Skin wound on back

There is irregular loss of pigment disrupting the skin

color pattern over the back. The margins of this region

are white, suggesting degeneration and scarring.
15

Emaciation and runting 

These newly metamorphosed leopard frogs have marked disparity in size. The center frog is within the normal size

range for a newly metamorphosed frog (3.74 cm snout to vent length, 4.2 gm). The frogs on the left (2.15 cm snout to

vent length, 0.7 gm) and right (2.45 cm snout to vent length, 1.0 gm) are extremely small and in poor body condition.

The frog on the left is considered emaciated with a very narrow body silhouette along the abdomen and flank. The

outline of the bones of shoulder, spine and pelvis can be easily defined through the skin and there is severe muscle

wasting which is most obvious along the legs. This muscle wasting makes the legs look very thin and the head looks

disproportionately large for the body size. 

11G

11E

Tuberculosis of the skin of a frog

This raised, tan, ulcerated skin mass resembles a

tumor but is the consequence of infection with the

species of mycobacteria which causes amphibian TB.

The mass is composed of characteristic inflammatory

cells that contain these bacteria.

11F

Eye opacity due to intraocular infection with an immature fluke

The lens region of the eye in this late-stage tadpole is

opaque and resembles a cataract. However, the opacity

in this eye is actually a live immature fluke. The

consequence of this infection on the post-metamorphic

frog is not known, but one might assume that the frog’s

vision would be obstructed.
16

References

Bolande, R. P. 1979. Developmental Pathology. American Journal of Pathology 94(3), pp. 627-638.

Carlson, B. M. 1994. Human Embryology and Developmental Biology. Chapter 11, Limb Development, Mosby-Year 

Book, Inc. pp. 182-203.

Duellman, E. and Trueb, L., 1996. Biology of Amphibians. The John Hopkins University Press, Baltimore, MD.

Gilbert, S.F. (ed). 1997. Development of the tetrapod limb. In: Developmental Biology, pp. 701-731. Sinauer Associates, 

Inc., Sunderland, Massachusetts. 

O’Rahilly, R., Muller, F. 1996. Human Embryology & Teratology, Second Edition, Wiley-Liss, Inc. pp. 10-15.

Meteyer, C.U., I. K. Loeffler, J. G. Burkhart, K. A., Converse, E. Green, J. C. Helgen, S. Kersten, R. Levey, L. EatonPoole, and J. F. Fallon. 2000b. Hind limb malformations in free–living Northern leopard frogs (Rane pipiens) from

Maine, Minnesota and Vermont suggest multiple etiologies. Teratology 60: 151–171.

Robbins, S. L., R. S. Cotran, V. Kumar. 1984. Congenital malformation. In Pathological Bases of Disease, S. L. Robbins, 

R. S. Cotran, V. Kumar (eds), W.B. Saunders Company, Philadelphia, PA, pp. 479-482.

Wise D. L., S. L. Beck, D. Beltrame, B. K. Beyer, I. Chahoud, R. L. Clark, R. Clark, A. M. Druga, M. H. Feuston, P. 

Guittin, S. M. Henwood, C. A. Kimmel, P. Lindstrom, A. K. Palmer, J. A. Petrere, H. M. Solomon, M. Yasuda, R. G.

York. 1997. Terminology of developmental abnormalities in common laboratory mammals (Version 1). Teratology

55:249-292.
L R

No Limb: Amelia

Incomplete Limb: (Ectromelia)

No knee (elbow): Ectromelia

of femur (humerus)

No foot (hand) or hock (wrist):

Ectromelia of tibiafibula

(radius and ulna)

Partial foot (hand) Hock

(wrist) joint but no toes:

Ectromelia of tibiale/fibulare 

Foot attached “directly” to

body No identifiable

proximal limb: Phocomelia

Complete Limb With 

Abnormal Long Bones 

L R

Skin Web

Band of skin crosses joint

Bone bridge

Sharp bend in mid–shaft bone

Rotation:

Primary rotation

no bone bridge or skin web

Secondary rotation

Caused by bone bridge or

skin web

Long bone shortened

Hemimelia of femur,

tibiafibula or tibiale/fibulare 

Proportionately short limb

Micromelia; short bones,

often reduced muscle mass

Complete Limb; Digits

Abnormal

L R

Entire toe missing

Ectrodactyly

Short toes

Brachydactyly

Multiple toes:

Entire duplication

Polydactyly

Partial duplication

Polyphalangy

Mixed pattern same toe:

Brachydactyly, and

polyphalangy

Multiple Limbs

Polymelia; Sketch (label, e.g.

A, B, C) describe these limbs

(referring to labels) including

site of limb origin, pairing,

limb function, completeness,

muscle development.

Miscellaneous

Small bone projection (sketch)

Other: Describe (sketch)

Key to Frog and Toad Malformations C.U. Meteyer, 2000

L and R refer to animal’s left and right

Malformation of limb see page 1;

Malformations of head, spine and skin, see page 2

Abnormality not malformation, see page 2

Limb Malformations Rear limb Forelimb (Forelimb nomenclature in parentheses)

Left Right Right Left

Dorsal view Ventral view

1
2

Head Shape

Small head microcephaly

Domed head

Eye

L R

Missing eye: anophthalmia

Small eye: microphthalmia

Iris abnormal color or shape

Iris absent 

Malpositioned eye

Mouth or Jaw Abnormal

No jaw: Agnathia

Lower (mandibular)

Upper (maxillary)

Cleft jaw 

Lower (mandibular)

Upper (maxillary)

Small jaw: micrognathia

Lower (mandibular)

Upper (maxillary)

Curved jaw

Absent tongue: Aglossia

Protruding tongue

Spine Malformations

Hunched back: Kyphosis

Curvature: Scoliosis

Extension of “spine” beyond

rump

Malformation: Abnormality not

malformation

Head (Craniofacial) Malformations

Skin Malformations

Pigment/color: Describe 

and sketch

Pigment lacking, translucent

Pattern abnormal

L R

Trauma Describe fracture,

laceration, amputation

Infectious 

Viral, bacterial, parasitic

Emaciation

Other

Unknown

Left Right Right Left

Dorsal view Ventral view

Lateral Right view Lateral Left view