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Smithsonian National Museum of Natural History
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Department of Vertebrate Zoology

Division of Amphibians & Reptiles

Oxyrhopus petola
Oxyrhopus petola Ecuador, Napo Province. Photographed by William W. Lamar
Cochranella midas
Crochranella midas Ecuador, Napo Province. Photographed by Roy McDiarmid


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History of Collection

There are several kinds of specimen preparations in our collection.  Most of our specimens are "wet" (stored in ethanol), but we also have dry skeletal specimens and glycerine-stored cleared and stained (C&S) skeletal specimens.  There are also specimens stored and preserved in formalin (mostly amphibian larvae), and histological microscope slides of tissues.

Wet about 547,000
Dry about 13,300
C&S about 4,200
Form about 7,700
Hist about 1,500

A single specimen may be a composite of various preparations.  An extreme example would be a frog with an ethanol-preserved skin and viscera, cleared and stained head, dry postcranial skeleton, histological slides of its reproductive tract, and frozen blood, liver, etc. stored as tissue sample.  This hypothetical specimen could also be a voucher for a publication, or other types of data such as photographs and vocalizations on audiotape, all of which are keyed and searchable on the data base.

Wet Collection

Our "wet" collection is stored in 70% ethanol (EtOH) and is by far the largest component of our collection.  Wet specimens were originally stored in ground glass jars and ceramic crocks, whereas small specimens are now stored in screw-top flint-glass jars with polypropylene lids or canning-style bailtop jars with synthetic gaskets, and large specimens are stored in stainless steel tanks.  Prior to the 1890s, most wet specimens were simply preserved in "alcohol" (i.e. rum, distilled wine, spirits, etc.) and were then stored in EtOH.  Currently, we 'fix' specimens in 10% formalin first, then transfer them to 70% EtOH for long-term storage.

Our largest wet specimen is a 3 m, 175 kg American crocodile in a tank at the MSC.  The smallest adult specimens are likely microhylid and leptodactylid frogs, smaller than pencil erasers.

The majority of our other preparations have been incorporated into the collection during the last 50 years.


The majority of our dry collection is skeletal material though there are a few skins (some old, stuffed skins and a few skins of very large specimens that were too big to preserve as wet specimens).

Cleared and Stained

The cleared and stained collection consists mostly of small and/or fragile specimens that would be damaged or disarticulated in the process of making dry skeletal preparations.  For the last 25 years most of our C&S specimens have been prepared using a double staining technique that stains the bones red and some types of cartilage blue.  The advantage of staining the cartilage blue is that a researcher can determine the relative positions of the adjoining bones, mineralization of growing bones (and therefore developmental stage of an individual), and see more detail in structures that contain substantial cartilaginous components, such as the hyoid apparatus and tadpole chondrocrania.


The formalin collection has been the fastest growing portion of our collection, having increased by over 500% in the last 25 years.  This collection consists primarily of amphibian larvae, particularly tadpoles, stored in 10% formalin.

Histological Slides

The bulk of our histological slide collection is made up of the voucher specimens for Ernest Wever's research on the structure of amphibian and reptile ears.  There are also vouchers for skeletochronology and reproductive studies.


The Division keeps both original working and archival copies of audiotapes, primarily of frog vocalizations, as vouchers for published works and future analyses.  Recently, copies of all tapes have also been transferred to CD.  Typically these frog calls are themselves vouchered; that is, they were recorded from individuals that are now specimens in our collection.  These recordings are an important taxonomic tool because frog calls are species-specific.


Division personnel and associated researchers routinely collect tissue samples when doing field work.  We do not store tissues as part of the permanent collections because the tissues are usually consumed by the analysis.  The specimen from which the tissue derives, however, is almost always preserved in the cataloged collection as a voucher for species verification.

(rev. June 2012)

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