Across nearly every ecosystem on Earth, biodiversity tends to follow a pattern in which there are a small handful of very common species and many, many more rare species. It would seem our knowledge of plants follows a similar pattern; we know a lot about a small group of species and very little to nothing about most others. Take, for example, a succulent relative of the milkweeds known to science as Whitesloanea crassa. Despite its occurrence in specialist succulent plant collections, we know next to nothing about the natural history of this species or if it even still exists in the wild at all.

Without flowers, one would be hard pressed to place this odd succulent within a family. Even when in bloom, proper analysis of its taxonomic affinity requires a close inspection of the floral morphology. What W. crassa exhibits is a highly derived morphology well-adapted to its xeric environment. Native to Somalia, it was said to grow on bare ground and its appearance supposedly matches the rocks that dominate its desert habitat. Never producing leaves or branches, the main body of W. crassa consists of a succulent, quadrangular stem that slowly grows upwards as it ages.

Flowers are produced in a dense inflorescence, which is most often situated near the base of the plant. Each flower is very showy at maturity, consisting of a fleshy, fused, 5-lobed corolla decorated in shades of pink and red. As far as I can tell, this is not one of stinkier members of the family. Though I have found pictures of flowers crawling with maggots, most growers fail to comment on any strong odors. In fact, aside from limited care instructions, detailed descriptions of the plant represent the bulk of the scientific information available on this odd species.

Maggots crawling around inside the flowers indicates this species mimics carrion as its pollination mechanism. Photo by: Flavio Agrosi

As I mentioned, it is hard to say whether this species still exists in the wild or not. The original mention of this plant in the literature dates back to 1914. A small population of W. crassa was found in northern Somalia and a few individuals were shipped overseas where they didn’t really make much of an impact on botanists or growers at that time. It would be another 21 years before this plant would receive any additional scientific attention. Attempts to relocate that original population failed but thanks to a handful of cultivated specimens that had finally flowered, W. crassa was given a proper description in 1935. After that time, W. crassa once again slipped back into the world of horticultural obscurity.

A few decades later, two additional trips were made to try and locate additional W. crassa populations. Botanical expeditions to Somalia in 1957 and again in 1986 did manage to locate a few populations of this succulent and it is likely that most of the plants growing in cultivation today are descended from collections made during those periods. However, trying to find any current information on the status of this plant ends there. Some say it has gone extinct, yet another species lost to over-collection and agriculture. Others claim that populations still exist but their whereabouts are kept as a closely guarded secret by locals. Though such claims are largely unsubstantiated, I certainly hope the latter is true and the former is not.

Our knowledge of W. crassa is thus restricted to what we can garner from cultivated specimens. It is interesting to think of how much about this species will remain a mystery simply because we have been unable to observe it in the wild. Despite these limitations, cultivation has nonetheless provided brief windows into it’s evolutionary history. Because of its rock-like appearance, it was assumed that W. crassa was related to the similar-looking members of the genus Pseudolithos. However, genetic analysis indicates that it is not all that closely related to this genus. Instead, W. crassa shares a much closer relationship to Huernia and Duvalia.

This is where the story ends unfortunately. Occasionally one can find cultivated individuals for sale and when you do, they are usually attached to a decent price tag. Those lucky enough to grow this species successfully seem to hold it in high esteem. If you are lucky enough to own one of these plants or to have at least laid eyes on one in person, cherish the experience. Also, consider sharing said experiences on the web. The more information we have on mysterious species like W. crassa, the better the future will be for species like this. With any luck, populations of this plant still exist in the wild, their locations known only to those who live nearby, and maybe one day a lucky scientist will finally get the chance to study its ecology a little bit better.

Photo Credits: [1] & Flavio Agrosi [2] [3] [4]

Further Reading: [1] [2]

Reconstructing extinct organisms based on fossils is no simple task. Rarely do paleontologists find complete specimens. More often, reconstructions are based on fragments of individuals found either near one another or at least in similar rock formations. This is especially true for plants as their growth habits frequently result in fragmentary fossilization. As such, fossilized plant remains of a single species are often described as distinct species until subsequent detective work pieces together a more complete picture.

Such was the case for the fossil remains of what were described as Krassilovia mongolica and Podozamites harrisii. Hailing from the Early Cretaceous (some 100-120 million years ago), Krassilovia was only known from oddly spiny cone scales and Podozamites was only known from strap-shaped leaves found in a remote region of Mongolia. Little evidence existed to suggest they belonged to the same plant. That is, until these structures were analyzed using scanning electron micrographs.

(A–C) Articulated seed cones, (D) Isolated cone axis, (E) Incomplete leafy shoot showing a cluster of three attached leaves, (F) Three detached strap-shaped leaves, G) Detail of A showing tightly imbricate interlocking bract-scale complexes, (H) Det… — (A–C) Articulated seed cones, (D) Isolated cone axis, (E) Incomplete leafy shoot showing a cluster of three attached leaves, (F) Three detached strap-shaped leaves, G) Detail of A showing tightly imbricate interlocking bract-scale complexes, (H) Detail of leaf apex showing converging veins, (I) Three isolated bract-scale complexes showing abaxial (top) and adaxial (bottom) surfaces, (J) Two isolated seeds showing narrow wings. [SOURCE]

These fossilized plant remains were preserved in such detail that microscopic anatomical features such as stomata were visible under magnification. By studying the remains of these plants as well as others, scientists discovered some amazing similarities in the stomata of Krassilovia and Podozamites. Unlike other plant remains associated with those formations, the Krassilovia cone scales and Podozamites leaves shared the exact same stomate morphology. Though not without some uncertainty, the odds that these two associated structures would share this unique morphological trait by chance is slim and suggests that these are indeed parts of the same plant.

The amazing discoveries do not end with stomata either. After countless hours of searching, fully articulated Krassilovia cones were eventually discovered, which finally put the strange spiky cone scales into context. It turns out those spiked scales interlocked with one another, with the two bottom spikes of one scale interlocking with the three top spikes of the scale below it. In life, such interlocking may have helped protect the developing seeds within until they had matured enough to be released. Also, the sheer volume of cone scales coupled with other minute anatomical details I won’t go into here indicate that, similar to Abies and Cedrus cones, Krassilovia cones completely fell apart when fully ripe.

Though not related, the cone scales of the extinct Krassilovia (left) show similarities with the cone scales of modern day Cryptomeria species (right). — Though not related, the cone scales of the extinct *Krassilovia* (left) show similarities with the cone scales of modern day *Cryptomeria* species (right).

Interestingly, the ability to resolve microscopic structures in these fossils has also provided insights into some modern day taxonomic confusion. It turns out that Krassilovia shares many minute anatomical similarities with present day Gnetales. Gnetales really challenge our perception of gymnosperms and their superficial resemblance to angiosperms have led many to suggest that they represent a clade that is sister to flowering plants. However, more recent molecular work has placed the extant members of Gnetales as sister to the pines. Evidence of shared morphological features between extinct conifers like Krassilovia and modern day Gnetales add some interesting support to this hypothesis. Until more concrete evidence is described and analyzed, the true evolutionary relationships among these groups will remain the object of heated debate for the foreseeable fture.

What we can say is that Krassilovia mongolica was one remarkable conifer. Its unique morphology clearly demonstrates that conifers were once far more diverse in form and function than they are currently. Even the habitat in which Krassilovia once lived is not the kind of place you can find thriving conifer communities today. Krassilovia once grew in a swampy habitat. However, whereas only a few extant conifers enjoy swamps, Krassilovia once shared its habitat with a wide variety of conifer species, the likes of which we are only just beginning to appreciate. I for one am extremely excited to see what new fossil discoveries will uncover in the future.

LISTEN TO EPISODE 300 OF THE IN DEFENSE OF PLANTS PODCAST TO LEARN MORE ABOUT THIS FOSSIL AND THE ECOSYSTEM IN WHICH IT ONCE EXISTED.

Photo Credits: [1] [2] [3]