Suborder Archaeobatrachia

Family Leiopelmatidae (Tailed frogs): Distribution is Old and New World, restricted to new Zealand and the Western United States. Fertilization is internal-- a rare condition in anurans. All species are oviparous, with one species having direct development. The specimen you will see in lab today is sometimes placed in its own family, Ascaphidae. The best character is the "tail", which is actually an extension of the cloaca in males.

MI species: none

Suborder Aglossa

Family Pipidae (Clawed frogs and Surinam toads): Distribution is Old and New World. Strictly aquatic. In some species, eggs become imbedded in the female's back, and young emerge as fully developed froglets. Good characters: large, broad feet, flattened body, dark "claws" on the tips of three of the hind toes. Incidentally, the tadpoles hatched aboard the space shuttle Endeavour a few years ago were members of this family.

MI species: none

Suborder Pelobatoidea

Family Pelobatidae (Spadefoot toads and horned toads): Old and New World. Spadefoot toads burrow underground in sandy soil and remain buried almost year-round, emerging briefly during the rainy season to feed and reproduce. They are remarkably resistant to dessication. Tadpoles develop quickly in temporary waters and sometimes develop specialized mouthparts for cannibalism in order to complete development quickly. Best character for spadefoots: dark "spade" on bottom of foot used for burrowing. Also, large, bulging eyes and short, stout body. For horned toads: fleshy projections shaped like "horns". (You may be wondering why these two groups of frogs are placed in the same family, and yet do not resemble each other at all. They possess skeletal features which are intermediate between primitive and advanced frogs which cause taxonomists to group them together. This is a great example of why osteology is so important!)

MI species: none

Suborder Neobatrachia

Family Bufonidae (True toads): Look at the distribution map in Halliday and Adler (p. 55), and then say "Wow!" This is about as worldwide as amphibian distribution gets. Adults are terrestrial; most species have a tadpole stage, but some have direct development. Best character: parotoid (not parotid) glands in shoulder region. Other good characters: extensive warts, short legs, lack of toe webbing, and cranial crests. For help distinguishing between bufonids and pelobatids, see Fig. 90 on p. 299 in your field guide. Size, shape, and spatial relationship of the parotoid glands and cranial crests can be used to distinguish between species of true toad (see Fig. 95, p. 308 in your field guide).

MI species:

Bufo americanus (American Toad)

Bufo woodhousii fowleri (Fowler's Toad)

Family Leptodactylidae ("Imitator" frogs): New World only. Widely variant natural history. Also, in terms of external morphology, there is so much diversity in this family that there are no really good characters. These frogs often resemble frogs in other families; the examples you will see in lab resemble small hylids. For another example, see plate 45 in your field guide. The white lipped frog strongly resembles members of the family Ranidae.

MI species: none

Family Hylidae (True tree frogs): Distribution includes the Old and New Worlds. Some species have direct development, others enclose eggs in foam nests which they make above water in the overhanging limbs of trees; when tadpoles hatch, they fall into the water below, where they live until they complete metamorphosis. Tree frogs can be distinguished by their long legs and long toes with adhesive toe disks. Toe disks may be difficult to see in smaller members of this family. Note: Two of the Michigan species of this family, Hyla versicolor and Hyla chrysoscelis, cannot be distinguished using external morphology, despite the efforts of several workers to find a way to do so. They can, however, be distinguished by examining their karyotypes (Hyla versicolor is tetraploid, while H. chrysoscelis is diploid) and by listening to their calls. You are not expected to tell them apart for your practical. In addition, the only reliable character for distinguishing the two subspecies of Pseudacris triseriata is the length of the tibia, which is slightly longer in P. t. triseriata than in P. t. maculata. It is interesting to compare them in the lab, since shorter legs are sometimes associated with colder climate. However, I do not expect you to tell these two subspecies apart for your practical.

MI species:

Acris crepitans blanchardi (Blanchard's Cricket Frog)

Pseudacris triseriata triseriata (Western Chorus Frog)

Pseudacris triseriata maculata (Boreal Chorus Frog)

Pseudacris crucifer ( Spring Peeper, also known as Hyla crucifer)

Hyla versicolor (Gray Treefrog)

Hyla chrysoscelis (Cope's Gray Treefrog)

Family Ranidae (True frogs): Like the bufonids, the ranids have an essentially worldwide distribution. They are riparian and have a normal aquatic tadpole stage. The largest known frog, the Goliath Frog, belongs to this family. Feet extensively webbed, tympanum well developed. Most species have a dorsolateral ridge. Sexual dimorphism: In three of the Michigan species, sex can be determined by the "tympanum rule": in males, the tympanum is larger than the eye, whereas in females the tympanum is the same size as the eye or a little smaller. Check your field guide to find out which ones these are, then examine the lab specimens to see the difference. You will need to be able to tell males from females for your lab practical.

MI species:

Rana catesbeiana (Bullfrog)

Rana clamitans (Green Frog)

Rana palustris (Pickerel Frog)

Rana pipiens (Northern Leopard Frog)

Rana septentrionalis (Mink Frog)

Rana sylvatica (Wood Frog)

Family Microhylidae (Narrow-mouthed Frogs): Old and New World. Some species have direct development. Also, some lay eggs and have tadpole stage in bromeliads. Members of this family are small and eat mostly ants. Good characters: smooth skin, small head with narrow mouth.

MI species: none

Family Dendrobatidae (Poison-Dart Frogs): New World only, restricted to tropical rain forests of Central and South America. Because of their brilliant colors, these frogs are extremely popular and are often used as symbols of the disappearing rain forests in which they live. The bright colors of dendrobatid frogs are an outstanding example of aposematic coloration, used to warn would-be predators of the extremely potent batrachotoxins which these tiny frogs produce. Many species of poison-dart frogs exhibit parental care limited exclusively to males, which is fairly rare among vertebrates. Eggs are commonly laid in bromeliads, and tadpoles are commonly transported on the backs of their parents to larger bodies of water to complete development. Like all amphibians, dendrobatids lose most of their coloration when preserved, and the best characters to look for in the lab are small size, long, slender legs, and tiny toe discs. Note: Although dendrobatid frogs are commonly referred to as poison-arrow frogs, it is more correct to refer to them as poison-dart frogs. Toxins harvested from the skin of some dendrobatids by tribes native to the rain forest have been used to coat the tips of small darts, which are shot from blowguns. Most toxins used in dart poisons are plant extracts, and the practice of using frogs for this purpose is not nearly as widespread as many people believe.

MI species: none

You are responsible for knowing the call of each of the Michigan anuran species. I recommend making a separate tape of just the Michigan anurans to make studying easier. You do not need to know the calls of Acris crepitans blanchardi or Pseudacris triseriata maculata because they are not included on the tape.