science

Holmiidae

Holmiidae is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Holmiidae rather than just read about it. In short: Holmiidae is a family of trilobites, that lived during the Lower Cambrian (Atdabanian). The Holmiidae is a diverse family of eight genera containing at least 17 species.

Key takeaways

Holmiidae belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Holmiidae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Holmiidae from memory before moving on to harder problems.

Reference excerpt

Holmiidae is a family of trilobites, that lived during the Lower Cambrian (Atdabanian). The Holmiidae is a diverse family of eight genera containing at least 17 species. It includes some of the earliest trilobites of Baltica. Holmiidae occur throughout Baltica (Scandinavia and the eastern seaboard of the Baltic Sea) and Western Laurentia (in the Great Basin of the US and northwestern Canada), and also in Morocco.

Taxonomy Hupé (1953) defined the Holmiidae as a subfamily (Holmiinae) within the Olenellidae containing Holmia, Kjerulfia and Bondonella. Harrington et al. (1959) excluded Kjerulfia, while assigning Schmidtiellus to it. Bergström (1973) included Holmia, Elliptocephala, Esmeraldina, Schmidtiellus and Wanneria. Repina (1979) assigned Holmia, Schmidtiellus, Kjerulfia, Elliptocephala, Bondonella, Andalusiana and Holmiella to the Holmiinae, that together with the monotypic Callaviinae comprised the Holmiidae. Palmer and Repina (1993) added Holmiella but excluded Kjerulfia, they assigned to the Callaviinae. Lieberman, who made cladistic analyses of the Olenellina and the included superfamilies, regards Andalusiana an advanced "Nevadioidea", Callavia and Bondonella as Judomioidea, and Elliptocephala and Wanneria stemgroup genera closely related to the common ancestor of the Holmiidae and the Biceratopsidae.

Genera Andalusiana Lotze 1958 Callavia Matthew 1897 Cambropallas Geyer 1993 Elliptocephala Esmeraldina Resser and Howell, 1938 Grandinasus Hollingsworth, 2006 Holmia Matthew, 1890 synonym Baltobergstroemia Holmiella Fritz, 1972 Iyouella Geyer and Palmer 1995 Kjerulfia Kiaer, 1917 Montezumaspis Hollingsworth, 2006 Palmettaspis Fritz, 1995 Schmidtiellus Moberg in Moberg and Segerberg, 1906

Relationships within the Holmiidae The eye ridges in Baltic and Moroccan Holmiidae (Holmia, Schmidtiellus) are wide, have a furrow atop the ridges, and the resulting inner band merges with the frontal lobe (L4) of the glabella without an axial furrow. This is interpreted as advanced compared with the arrangement of the simple ocular lobes of Laurentian holmiids, which are separated from the L4 by a prominent axial furrow around the glabellar outline.

Description As with most early trilobites, Holmiidae have an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the Olenellina suborder, the Holmiidae lack dorsal sutures in the cephalon. Like all other members of the Olenelloidea superfamily, the eye-ridges spring from the back of the frontal lobe (L4) of the central area of the cephalon (or glabella). Specifically for the Holmiidae are the following diagnostic characters. The glabella is straight-sided to somewhat constricted and mostly expands forward. The frontal lobe (or L4) is usually broad and rounded. The furrows that separate the lobes are usually curved, moderately incised, and rarely completely cross the midline. The eye ridges of Baltic holmiids are often wide with an ocular furrow, inner band merging with L4 without axial furrow. Laurentian holmiids (Montezumaspis, Palmetaspis, Grandasinus, Esmeraldina and Holmiella) have unfurrowed ocular lobes separated from L4 by axial furrow. The cephalon carries so called genal spines at the corner between the half circle front/side margin and the back margin that is roughly perpendicular to the midline. These spines extend back to at least the fourth thorax segment (T4), counted front to back. The back margin of the cephalon normally carries a node or spine (or intergenal spine), straight behind the point the eye ridge is furthest from the midline or even somewhat further out. Back margin of cephalon inside the intergenal angle transverse or directed posteriorly. The third thorax segment (T3) is not larger than the neighboring segments and does not carry larger spines. Anterior thoracic pleural spines weakly to strongly thornlike except in Kjerulfia and Grandinasus.

References

Illustrations

Holmiidae: Holmia kjerulfi — Holmia kjerulfi

Worked examples

Example 1 — a first encounter with Holmiidae

Start with the simplest possible case. Write down what Holmiidae claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Holmiidae before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Holmiidae ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Holmiidae

In research: Holmiidae appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Holmiidae in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Holmiidae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cambrian first appearances, Cambrian trilobites, Fossils of Canada, so understanding it makes those chapters shorter.
In everyday life: Look for Holmiidae outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Holmiidae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Holmiidae means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Holmiidae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Holmiidae in simple terms?

Holmiidae is a family of trilobites, that lived during the Lower Cambrian (Atdabanian). The Holmiidae is a diverse family of eight genera containing at least 17 species.

Why does Holmiidae matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Holmiidae?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Holmiidae.