Phytosaurs first appeared during the Carnian age, evolving from an unknown crurotarsan ancestor.
There are no clear intermediate forms, as even the earliest known phytosaurs are highly specialized aquatic animals, unlike most contemporary archosauriforms that were terrestrial.
However, a recent study has suggested that Diandongosuchus is a basal phytosaur.
If this is the case, this taxon offers more of a bridge between phytosaurs and earlier Archosauriformes.

The earliest phytosaurs are traditionally classified in the genus Paleorhinus, now thought to be polyphyletic.
Parasuchus and related basal species were widely distributed, meaning that phytosaurs dispersed across Pangea early on and there were probably few geographical barriers for their distribution; only in the southernmost regions are they rare, possibly due to increased aridity.

A somewhat more advanced and larger form, Angistorhinus appears at the same time or soon after.
Later in the Carnian, both these animals were replaced by more specialised forms like Rutiodon, Leptosuchus, and the huge Smilosuchus (Lucas 1998).
The Carnian-Norian extinction meant that these animals died off, and the Early Norian sees new genera like Nicrosaurus and Pseudopalatus, both of which belong to the most derived clade of phytosaurs, the Pseudopalatinae.
Later in the middle Norian the advanced and specialised fish-eater Mystriosuchus appears.
Fossil remains of this widespread animal is known from Germany, northern Italy, and Thailand.
Finally the large Redondasaurus in south-west North America and the long-snouted (altirostral) Angistorhinopsis ruetimeyeri in Europe continued the group into the Rhaetian.
Phytosaur footprints (the ichnotaxon Apatopus) are also known from the latest Rhaetian of the East Coast of USA (the Newark Supergroup) (Olsen et al.
2002).
This indicates that phytosaurs continued as successful animals until the very end of the Triassic, when, along with many other large crurotarsan reptiles, they were killed off by the end Triassic extinction event, about 200 Ma ago.

There have been reports of phytosaur remains found in lowermost Jurassic rocks.
Several teeth from Early Jurassic deposits in France have been identified as phytosaur teeth, but other studies argue they have either been misidentified or were reworked from Late Triassic into Early Jurassic deposits.
In 1951, a partial upper jaw was discovered in the Early Jurassic Lower Lufeng Series in China and described as a new genus of phytosaur, Pachysuchus, but a study in 2012 reinterpreted the fossil as a sauropodomorph dinosaur.

A fragment of a lower jaw from a longirostrine archosaur has been described from early Hettangian strata in the town of Watchet in Somerset, England.
While teleosaurid thalattosuchians had similar longirostrine jaws to phytosaurs and were common in the Jurassic, they do not appear in the earliest Jurassic rocks.
The mandible is more similar to those of known phytosaurs than to thalattosuchians, and likely belongs to a phytosaur closely related to the genus Mystriosuchus.
The presence of phytosaurs in the earliest Jurassic may have prevented thalattosuchians from occupying similar ecological niches at that time.
However, more recent work suggests that the jaw fragment came from a pre-Hettangian rock unit, and is therefore Late Triassic in age.
Phytosaurs first appeared during the Carnian age, evolving from an unknown crurotarsan ancestor. There are no clear intermediate forms, as even the earliest known phytosaurs are highly specialized aquatic animals, unlike most contemporary archosauriforms that were terrestrial. However, a recent study has suggested that Diandongosuchus is a basal phytosaur. If this is the case, this taxon offers more of a bridge between phytosaurs and earlier Archosauriformes.
The earliest phytosaurs are traditionally classified in the genus Paleorhinus, now thought to be polyphyletic. Parasuchus and related basal species were widely distributed, meaning that phytosaurs dispersed across Pangea early on and there were probably few geographical barriers for their distribution; only in the southernmost regions are they rare, possibly due to increased aridity.
A somewhat more advanced and larger form, Angistorhinus appears at the same time or soon after. Later in the Carnian, both these animals were replaced by more specialised forms like Rutiodon, Leptosuchus, and the huge Smilosuchus (Lucas 1998). The Carnian-Norian extinction meant that these animals died off, and the Early Norian sees new genera like Nicrosaurus and Pseudopalatus, both of which belong to the most derived clade of phytosaurs, the Pseudopalatinae. Later in the middle Norian the advanced and specialised fish-eater Mystriosuchus appears. Fossil remains of this widespread animal is known from Germany, northern Italy, and Thailand. Finally the large Redondasaurus in south-west North America and the long-snouted (altirostral) Angistorhinopsis ruetimeyeri in Europe continued the group into the Rhaetian. Phytosaur footprints (the ichnotaxon Apatopus) are also known from the latest Rhaetian of the East Coast of USA (the Newark Supergroup) (Olsen et al. 2002). This indicates that phytosaurs continued as successful animals until the very end of the Triassic, when, along with many other large crurotarsan reptiles, they were killed off by the end Triassic extinction event, about 200 Ma ago.
There have been reports of phytosaur remains found in lowermost Jurassic rocks. Several teeth from Early Jurassic deposits in France have been identified as phytosaur teeth, but other studies argue they have either been misidentified or were reworked from Late Triassic into Early Jurassic deposits. In 1951, a partial upper jaw was discovered in the Early Jurassic Lower Lufeng Series in China and described as a new genus of phytosaur, Pachysuchus, but a study in 2012 reinterpreted the fossil as a sauropodomorph dinosaur.
A fragment of a lower jaw from a longirostrine archosaur has been described from early Hettangian strata in the town of Watchet in Somerset, England. While teleosaurid thalattosuchians had similar longirostrine jaws to phytosaurs and were common in the Jurassic, they do not appear in the earliest Jurassic rocks. The mandible is more similar to those of known phytosaurs than to thalattosuchians, and likely belongs to a phytosaur closely related to the genus Mystriosuchus. The presence of phytosaurs in the earliest Jurassic may have prevented thalattosuchians from occupying similar ecological niches at that time. However, more recent work suggests that the jaw fragment came from a pre-Hettangian rock unit, and is therefore Late Triassic in age.
Phytosaur