Archaeamphora

Archaeamphora longicervia is an extinct species of pitcher plant bearing close affinities to extant members of the family Sarraceniaceae. Fossil material assigned to this taxon originates from the Early Cretaceous Yixian Formation in northeastern China.

A. longicervia is the earliest known carnivorous plant and represents the only fossil record of pitcher plants. Furthermore, the monotypic Archaeamphora is one of the three oldest known genera of angiosperms (flowering plants). Li (2005) notes that "the existence of a so highly derived Angiosperm in the Early Cretaceous suggests that Angiosperms should have originated much earlier, maybe back to 280 mya as the molecular clock studies suggested".

Etymology
The generic name Archaeamphora is derived from the Greek: αρχαίος, archaios, combining form in Latin archae- and the Greek amphoreus (pitcher). The specific name longicervia is derived from the Latin longus (long) and cervicarius (with a neck). The latter refers to the characteristic constriction in the pitchers of this species.

Fossil material
All known fossil material of A. longicervia originates from the Jianshangou Formation in Beipiao, western Liaoning, China. These Early Cretaceous beds constitute the lower part of the Yixian Formation, which is dated at 124.6 million years old. Nine specimens of A. longicervia have been found, including holotype CBO0220 and paratype CBO0754.

Description
A. longicervia was a herbaceous plant growing to around 5 cm in height. The stem, at least 21 mm long and 1.2 mm wide, bore distinctive vertical ridges and grooves. Pitchers were ascidiate in form and 30 to 40 mm long. Mature pitchers and underdeveloped pitchers or phyllodia-like leaves were arranged spirally around the stem. Pitchers consisted of a tubular base, expanded middle section, constriction around the mouth, and a vertical, spoon-shaped lid. A single wing ran down the adaxial side of each pitcher. Three to five parallel major veins were present on the pitchers, along with a few intercostal veins and numerous small veinlets.

Two unusual bag-like structures were present on each pitcher, one on either side of the central wing. Similar but semi-circular structures were found on the margin of the lid. These structures exhibited strong yellow-green intrinsic fluorescence when exposed to 500 nm wavelength light.

Tiny glands, approximately 4 µm (micrometers) in diameter, were found on the inner surface of the pitchers and partially embedded in the grooves along the veins. These also showed very strong golden-yellow fluorescence.

A single seed was found intimately associated with the fossil material of A. longicervia and is presumed to belong to the same species. It is winged and reticulate-tuberculate in morphology, closely resembling the seeds of Sarraceniaceae taxa. The seed is oval-shaped, covered with black-brown warts, and measures 0.9 mm by 1.25 mm.

Taxonomy
The fossil material of A. longicervia was subjected to chemical analysis for oleanane, considered a key marker differentiating angiosperms from gymnosperms. Oleanane was detected in the pitcher plant specimens, suggesting that they belong to the angiosperms.

Several morphological features of A. longicervia suggest a close relationship to Sarraceniaceae. Both taxa exhibit one or two pitcher wings, a smooth peristome, and pitchers that extend vertically from the top of a short petiole.

Li (2005) suggests that A. longicervia is morphologically similar to modern Sarracenia purpurea. It shares with this species the spiral arrangement of its pitchers and phyllodia-like tubular leaves with parallel major veins. A. longicervia also shows close affinity to species of the genus Heliamphora in having pitchers with a long neck and upright lid. Of particular note is the similarity between the thick semi-circular structures on the lid of A. longicervia and the large nectar-secreting "spoon" present on the upper posterior portion of Heliamphora exappendiculata pitchers.

Li (2005) mentions the discovery of another type of pitcher plant from the same formation. This variety differs from the type material of A. longicervia in having pitchers that lack any constriction before the mouth, instead gradually expanding from the petiole into a hollow trumpet-like shape. He suggests that it "should be a different species" from A. longicervia. An intermediate form with a wider neck is also reported, suggesting that pitcher plants were already a diversified group in the Early Cretaceous.

Habitat
The area inhabited by A. longicervia is thought to have experienced significant climatic fluctuations during the Early Cretaceous, ranging from arid or semi-arid to more humid conditions. The substrate in the region was mostly composed of lacustrine sediments and volcanic rocks.