'creeping animal from Hyner') is an extinct genus of early four-limbed vertebrate that lived in the rivers and ponds of Pennsylvania during the Late Devonian period, around 365 to 363 million years ago.

Hynerpeton is known for being the first Devonian four-limbed vertebrate discovered in the United States, as well as possibly being one of the first to have lost internal (fish-like) gills.

The inner surface of this shoulder bone possesses an array of depressions believed to have been attachment points for a unique set of powerful muscles around the chest.

Devonian animals like Hynerpeton, Ichthyostega, and Acanthostega are excluded from the crown group Tetrapoda, since they evolved prior to the common ancestor of modern amphibians (Lissamphibia), reptiles, mammals, and birds.

Hynerpeton hails from the Red Hill fossil site, which, during the Late Devonian, was a warm floodplain inhabited by a diverse ecosystem of aquatic fish and terrestrial invertebrates.

Some paleontologists have proposed that animals like Hynerpeton made use their amphibious lifestyle to find shallow pools where they could spawn, isolated from predatory fish which inhabited the deeper rivers.

This fossil, designated ANSP 20053, is now considered the holotype specimen of Hynerpeton, which Daeschler and his colleagues formally named in an article published by Science Magazine in 1994.

[4] In 2000, a pair of jaw bones were assigned to a second genus, Densignathus,[5] and other studies have argued that several additional unnamed taxa were present at the site, including possibly the oldest known whatcheeriid.

These fossils, which had not been previously noted in the scientific literature, included a jugal (cheek bone), belly scutes, and a portion of the mandible (lower jaw).

They noted that most fossils were assigned to Hynerpeton based on their close proximity to the point where the original endochondral shoulder girdle was discovered.

However, they argued that, since there were other unique animals (i.e. Densignathus, the owner of the unusual humerus, and whatcheerids) close to this point, proximity was not a sufficient reason to consider these referrals valid.

Although a lack of sufficient fossil material makes it unwise to come to specific conclusions about the anatomy of Hynerpeton, the structure of the preserved endochondral shoulder girdle offers some information on its classification.

The rear-pointing "blade" is formed by the scapulocoracoid, a plate-like bone which also possesses the glenoid fossa (shoulder socket) along its rear edge and in later tetrapods would separate into the scapula and coracoid.

In addition, the upper portion of the cleithrum is expanded and slightly tilted forwards, a derived character similar to Tulerpeton and true tetrapods.

[1] These characteristics combined seem to support the idea that Hynerpeton had very powerful muscles attached to the scapulocoracoid portion of the endochondral shoulder girdle.

[1] As these features are unknown in other stem- and crown-tetrapods, it is likely that Hynerpeton's musculature was used for some unique, experimental form of movement that did not survive the Devonian.

[10] Daeschler et al. (1994) considered the loss of the postbranchial lamina to be a derived feature indicating that Hynerpeton was more "advanced" than Acanthostega.

[12] Likewise, "Ichthyostegalia" has been abandoned in the age of cladistics due to being an evolutionary grade leading to true tetrapods, rather than a relations-based clade.

[13] The traditional, non-cladistic definition of Tetrapoda, which begins at the earliest limbed vertebrates, is roughly equivalent to a clade named Stegocephali, which is defined as all animals more closely related to temnospondyls than to Pandericthys.

Early arachnids (Gigantocharinus), millipedes (Orsadesmus), and undescribed scorpions were among the few fully terrestrial members of the Red Hill fauna.

[17] The depositional environment and fauna of the Red Hill site offered new hypotheses for the questions on why and how terrestriality evolved in stem-tetrapods.

In this subtropical modern environment experiencing wet and dry seasons, spawning golden perch (Macquaria ambigua) take refuge in oxbow lakes to escape larger, faster murray cod (Maccullochella peeli) in the main river channel.