How To Identify a Cactus

The columnar saguaro cactus.  Note the huge column like shape and ribs lined with spines traversing from the bottom to top.

Cacti are one of the most diverse and interesting plant families in the plant kingdom.  Cacti are native only to North and South America but are prized worldwide by plant enthusiasts.  I once worked with a PH.D who was from England but came to the United States specifically to work with cacti.  While you can go to just about any botanical garden in the world to observe cacti, the Southwestern United States and Mexico are probably the best places to observe cacti in the wild (in North America at least).  Within the United States, cacti can be found in the wild in just about every state.  Where I grew-up in Iowa, every once in awhile I would come across plains prickly pears growing in a dry prairie.  Now, living in the Southwest I come across cacti every single day.  The Sonoran Desert is loaded with all kinds of different cacti ranging from the 50 foot Saguaro cactus to the six inch tall pincushion.  Cacti are really not that difficult to identify, at least to the genus or "group" level.  Just about anyone can learn the major groups of cacti simply by looking at three major traits; the shape, ribs, and spines.

Barrel cacti in foreground.  Named after their barrel like shape.  Barrel cacti also have ribs lined with spines.

Shape is possibly the easiest and best way to categorize a cactus.  The most common cactus group is the prickly pears.  These cacti have stems that are sectioned into flat, pear or pancake shaped pads.  The overall prickly pear plant is joined together by these pads typically forming a shrub shape.  Cholla cacti are similar in that the plant is made up of sections, but instead of these sections being flat and pear shaped, they are cylindrical, and the overall plant also is shrub shaped.  Barrel cacti are barrel shaped.  Columnar cacti such as saguaros form tall columns. Tiny pincushion cacti are small and often shaped like an actual pincushion.  Hedgehog cacti are sort of like small columnar cacti that only grow a few feet tall at most, with the small stems bunching together.

A cylindrical cholla cactus section.

Ribs are the next important way of identifying a cactus.  Saguaros and other columnar cacti have long ribs or pilleates that stretch from the bottom of the cactus to the top.  Hedgehogs and barrels also have ribs.  Pincushions, prickly pears, and chollas do not have ribs. 

Prickly pear cactus with flat pear shaped sections.

Lastly spines.  Spines don't always help us distinguish between different groups of cacti but are extremely useful in determining the actual species of cacti.  A few spines like the tiny hairlike glochid are only found on prickly pears.  Glochids are the tiny spines that get stuck in your skin and have to be taken out with a tweezers.  Pincushions typically have tons of white spins which helps give them a "pincushion" like appearance.  Spine color, number, and shape are essential in learning to distinguish specific species of cacti.

Hedgehog cactus

Pincushion cactus.

Bringing Back the Dinosaurs... Sort Of...

Picture of a hadrosaur based off of findings from the dinosaur mummy "Leonardo".

In our last post we discussed how it has recently been discovered that some dinosaur fossils contain remnants of soft dinosaur tissue. In this post we will discuss the discovery of a fossilized dinosaur mummy.  Specifically, this dinosaur is a hydrosaur, or a duckbilled dinosaur, that died and was quickly buried in sediments before it could decay.  The burial process mummified the dinosaur, preventing decay and eventually the mummy was fossilized.  This dinosaur mummy is different from say human Egyptian mummies in that the dinosaur is actually fossilized and rock.  Egyptian mummies are simply well preserved tissues of the human that died.  As a result of the dinosaur mummy fossilizing, all of the parts of the dinosaur present in the mummy are still present today in rock form.  The process of fossilization of dinosaur mummies is exceedingly rare and have only been found a handful of times.  The awesome thing about mummies is that they preserve the soft tissues such as internal organs or skin which normally decay away long before any scientist can observe them.  The difficulty with fossilized mummies though is the fact that all of the soft tissues are now actually rock, which obviously is extremely difficult to dissect.  The documentary movie "Secrets of the Dinosaur Mummy" shows how modern day paleontologists "dissected" Leonardo without hacking him up.  The movie is a great demonstration of real scientists doing real science.  As a result of the "dissection", the scientists were able to find out all kinds of interesting biology about the dinosaur.  Huge changes in what we believe about dinosaurs in how they look and how their body functions have come about because of the investigation shown in this movie.  Also interesting, since the movie has been filmed, soft tissues like we talked about in our last post also have been found in Leonardo. 

Secrets of the Dinosaur Mummy
 

Actual fossilized dinosaur mummy "Leonardo".

Is Jurassic Park Possible? Bringing Back the Dinosaurs

Dinosaur soft tissue found in a fossilized T-Rex leg bone.

Is Jurassic Park really possible?  For nearly twenty years scientists have been telling us that the science behind the movie Jurassic Park is possible in theory, but not really possible in practice.  Why?  No one has ever or would ever be able to find intact dinosaur DNA from ancient fossilized bones, or mosquitoes for that matter.  Oddly though, about the time the movie was coming out, a paleontologist discovered the remains of some organic soft dinosaur tissue in a fossilized dinosaur bone.  How in the world would tissue survive such long periods of time and the fossilization process?  The answer to that question is that no one really knows, but several scientists working independently of each other have been able to verify the presence of dinosaur tissues in fossilized bones.  Organic molecules, including blood cells, have been found and confirmed in these specimens.  These samples open up a totally new area of paleontology and biology that has previously never been open for scientific examination before.  For example, through the examination of protein sequences, specifically collagin, scientists have been able to find that dinosaurs were closely related to birds.   Several different proteins have also been found in these fossils.  These proteins may open doors to understanding dinosaur physiology such as if they were warm or cold blooded.  Currently though, the field of studying ancient tissues from fossilized specimens is still highly controversial.  Even though there has been a lot of evidence to support the existence of this tissue and that it is not simply environmental contamination, the fact remains that it is still nearly unbelievable that organic soft tissues would survive decay over such long periods of time.  Though proteins have been found, no intact DNA has been found.  This makes sense considering protein molecules are significantly more stable than DNA.  So unfortunately, the search for dinosaur DNA and for Jurassic Park continues.  But with this discovery, we will get a lot closer to determining what a real dinosaur was like and what a real Jurassic Park would be like.

http://www.smithsonianmag.com/science-nature/dinosaur.html

In my next post I will discuss another, even more recent dinosaur finding which is even more amazing than this discovery.